diff --git a/mozilla/layout/generic/nsILineIterator.h b/mozilla/layout/generic/nsILineIterator.h
new file mode 100644
index 00000000000..3beeb4bf7df
--- /dev/null
+++ b/mozilla/layout/generic/nsILineIterator.h
@@ -0,0 +1,89 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * The contents of this file are subject to the Netscape Public License
+ * Version 1.0 (the "License"); you may not use this file except in
+ * compliance with the License.  You may obtain a copy of the License at
+ * http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS"
+ * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.  See
+ * the License for the specific language governing rights and limitations
+ * under the License.
+ *
+ * The Original Code is Mozilla Communicator client code.
+ *
+ * The Initial Developer of the Original Code is Netscape Communications
+ * Corporation.  Portions created by Netscape are Copyright (C) 1998
+ * Netscape Communications Corporation.  All Rights Reserved.
+ */
+#ifndef nsILineIterator_h___
+#define nsILineIterator_h___
+
+#include "nsISupports.h"
+
+/* a6cf90ff-15b3-11d2-932e-00805f8add32 */
+#define NS_ILINE_ITERATOR_IID \
+ { 0xa6cf90ff, 0x15b3, 0x11d2,{0x93, 0x2e, 0x00, 0x80, 0x5f, 0x8a, 0xdd, 0x32}}
+
+// Line iterator API.
+//
+// Lines are numbered from 0 to N, where 0 is the top line and N is
+// the bottom line.
+//
+// NOTE: while you can get this interface by doing a slezy hacky
+// QueryInterface on block frames, it isn't like a normal com
+// interface: its not reflexive (you can't query back to the block
+// frame) and unlike other frames, it *IS* reference counted so don't
+// forget to NS_RELEASE it when you are done with it!
+
+class nsILineIterator : public nsISupports {
+public:
+  NS_DEFINE_STATIC_IID_ACCESSOR(NS_ILINE_ITERATOR_IID)
+
+  // Return the number of lines in the block.
+  NS_IMETHOD GetNumLines(PRInt32* aResult) = 0;
+
+  // Return the prevailing direction for the line. aIsRightToLeft will
+  // be set to PR_TRUE if the CSS direction property for the block is
+  // "rtl", otherwise aIsRightToLeft will be set to PR_FALSE.
+  NS_IMETHOD GetDirection(PRBool* aIsRightToLeft) = 0;
+
+  // Return structural information about a line. aFirstFrameOnLine is
+  // the first frame on the line and aNumFramesOnLine is the number of
+  // frames that are on the line. If the line-number is invalid then
+  // aFirstFrameOnLine will be nsnull and aNumFramesOnLine will be
+  // zero. For valid line numbers, aLineBounds is set to the bounding
+  // box of the line (which is based on the in-flow position of the
+  // frames on the line; if a frame was moved because of relative
+  // positioning then its coordinates may be outside the line bounds).
+  NS_IMETHOD GetLine(PRInt32 aLineNumber,
+                     nsIFrame** aFirstFrameOnLine,
+                     PRInt32* aNumFramesOnLine,
+                     nsRect& aLineBounds) = 0;
+
+  // Given a frame thats a child of the block, find which line its on
+  // and return that line index into aIndexResult. aIndexResult will
+  // be set to -1 if the frame cannot be found.
+  NS_IMETHOD FindLineContaining(nsIFrame* aFrame,
+                                PRInt32* aLineNumberResult) = 0;
+
+  // Given a Y coordinate relative to the block that provided this
+  // line iterator, find the line that contains the Y
+  // coordinate. Returns -1 in aLineNumberResult if the Y coordinate
+  // is above the first line. Returns N (where N is the number of
+  // lines) if the Y coordinate is below the last line.
+  NS_IMETHOD FindLineAt(nscoord aY,
+                        PRInt32* aLineNumberResult) = 0;
+
+  // Given a line number and an X coordinate, find the frame on the
+  // line that is nearest to the X coordinate. The
+  // aXIsBeforeFirstFrame and aXIsAfterLastFrame flags are updated
+  // appropriately.
+  NS_IMETHOD FindFrameAt(PRInt32 aLineNumber,
+                         nscoord aX,
+                         nsIFrame** aFrameFound,
+                         PRBool* aXIsBeforeFirstFrame,
+                         PRBool* aXIsAfterLastFrame) = 0;
+};
+
+#endif /* nsILineIterator_h___ */
diff --git a/mozilla/layout/html/base/src/nsILineIterator.h b/mozilla/layout/html/base/src/nsILineIterator.h
new file mode 100644
index 00000000000..3beeb4bf7df
--- /dev/null
+++ b/mozilla/layout/html/base/src/nsILineIterator.h
@@ -0,0 +1,89 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * The contents of this file are subject to the Netscape Public License
+ * Version 1.0 (the "License"); you may not use this file except in
+ * compliance with the License.  You may obtain a copy of the License at
+ * http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS"
+ * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.  See
+ * the License for the specific language governing rights and limitations
+ * under the License.
+ *
+ * The Original Code is Mozilla Communicator client code.
+ *
+ * The Initial Developer of the Original Code is Netscape Communications
+ * Corporation.  Portions created by Netscape are Copyright (C) 1998
+ * Netscape Communications Corporation.  All Rights Reserved.
+ */
+#ifndef nsILineIterator_h___
+#define nsILineIterator_h___
+
+#include "nsISupports.h"
+
+/* a6cf90ff-15b3-11d2-932e-00805f8add32 */
+#define NS_ILINE_ITERATOR_IID \
+ { 0xa6cf90ff, 0x15b3, 0x11d2,{0x93, 0x2e, 0x00, 0x80, 0x5f, 0x8a, 0xdd, 0x32}}
+
+// Line iterator API.
+//
+// Lines are numbered from 0 to N, where 0 is the top line and N is
+// the bottom line.
+//
+// NOTE: while you can get this interface by doing a slezy hacky
+// QueryInterface on block frames, it isn't like a normal com
+// interface: its not reflexive (you can't query back to the block
+// frame) and unlike other frames, it *IS* reference counted so don't
+// forget to NS_RELEASE it when you are done with it!
+
+class nsILineIterator : public nsISupports {
+public:
+  NS_DEFINE_STATIC_IID_ACCESSOR(NS_ILINE_ITERATOR_IID)
+
+  // Return the number of lines in the block.
+  NS_IMETHOD GetNumLines(PRInt32* aResult) = 0;
+
+  // Return the prevailing direction for the line. aIsRightToLeft will
+  // be set to PR_TRUE if the CSS direction property for the block is
+  // "rtl", otherwise aIsRightToLeft will be set to PR_FALSE.
+  NS_IMETHOD GetDirection(PRBool* aIsRightToLeft) = 0;
+
+  // Return structural information about a line. aFirstFrameOnLine is
+  // the first frame on the line and aNumFramesOnLine is the number of
+  // frames that are on the line. If the line-number is invalid then
+  // aFirstFrameOnLine will be nsnull and aNumFramesOnLine will be
+  // zero. For valid line numbers, aLineBounds is set to the bounding
+  // box of the line (which is based on the in-flow position of the
+  // frames on the line; if a frame was moved because of relative
+  // positioning then its coordinates may be outside the line bounds).
+  NS_IMETHOD GetLine(PRInt32 aLineNumber,
+                     nsIFrame** aFirstFrameOnLine,
+                     PRInt32* aNumFramesOnLine,
+                     nsRect& aLineBounds) = 0;
+
+  // Given a frame thats a child of the block, find which line its on
+  // and return that line index into aIndexResult. aIndexResult will
+  // be set to -1 if the frame cannot be found.
+  NS_IMETHOD FindLineContaining(nsIFrame* aFrame,
+                                PRInt32* aLineNumberResult) = 0;
+
+  // Given a Y coordinate relative to the block that provided this
+  // line iterator, find the line that contains the Y
+  // coordinate. Returns -1 in aLineNumberResult if the Y coordinate
+  // is above the first line. Returns N (where N is the number of
+  // lines) if the Y coordinate is below the last line.
+  NS_IMETHOD FindLineAt(nscoord aY,
+                        PRInt32* aLineNumberResult) = 0;
+
+  // Given a line number and an X coordinate, find the frame on the
+  // line that is nearest to the X coordinate. The
+  // aXIsBeforeFirstFrame and aXIsAfterLastFrame flags are updated
+  // appropriately.
+  NS_IMETHOD FindFrameAt(PRInt32 aLineNumber,
+                         nscoord aX,
+                         nsIFrame** aFrameFound,
+                         PRBool* aXIsBeforeFirstFrame,
+                         PRBool* aXIsAfterLastFrame) = 0;
+};
+
+#endif /* nsILineIterator_h___ */