From de3dca4e6076fb215fe0412c600ae6bf41511f21 Mon Sep 17 00:00:00 2001
From: "bzbarsky%mit.edu"
 <bzbarsky%mit.edu@18797224-902f-48f8-a5cc-f745e15eee43>
Date: Sat, 21 Jul 2007 03:00:03 +0000
Subject: [PATCH] Don't generate state keys at all, if there's nothing to get. 
 Bug 388387, r+sr=sicking.

git-svn-id: svn://10.0.0.236/trunk@230408 18797224-902f-48f8-a5cc-f745e15eee43
---
 .../content/html/content/src/nsGenericHTMLElement.cpp | 11 +++++++++--
 .../content/html/content/src/nsGenericHTMLElement.h   |  3 +++
 mozilla/layout/base/nsILayoutHistoryState.h           |  9 +++++++--
 mozilla/layout/base/nsLayoutHistoryState.cpp          |  7 +++++++
 4 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/mozilla/content/html/content/src/nsGenericHTMLElement.cpp b/mozilla/content/html/content/src/nsGenericHTMLElement.cpp
index 6b56cd33e45..44a96025745 100644
--- a/mozilla/content/html/content/src/nsGenericHTMLElement.cpp
+++ b/mozilla/content/html/content/src/nsGenericHTMLElement.cpp
@@ -1733,7 +1733,7 @@ nsGenericHTMLElement::GetPrimaryPresState(nsGenericHTMLElement* aContent,
 
   nsCOMPtr<nsILayoutHistoryState> history;
   nsCAutoString key;
-  GetLayoutHistoryAndKey(aContent, getter_AddRefs(history), key);
+  GetLayoutHistoryAndKey(aContent, PR_FALSE, getter_AddRefs(history), key);
 
   if (history) {
     // Get the pres state for this key, if it doesn't exist, create one
@@ -1752,6 +1752,7 @@ nsGenericHTMLElement::GetPrimaryPresState(nsGenericHTMLElement* aContent,
 
 nsresult
 nsGenericHTMLElement::GetLayoutHistoryAndKey(nsGenericHTMLElement* aContent,
+                                             PRBool aRead,
                                              nsILayoutHistoryState** aHistory,
                                              nsACString& aKey)
 {
@@ -1771,6 +1772,11 @@ nsGenericHTMLElement::GetLayoutHistoryAndKey(nsGenericHTMLElement* aContent,
     return NS_OK;
   }
 
+  if (aRead && !(*aHistory)->HasStates()) {
+    NS_RELEASE(*aHistory);
+    return NS_OK;
+  }
+
   //
   // Get the state key
   //
@@ -1801,7 +1807,8 @@ nsGenericHTMLElement::RestoreFormControlState(nsGenericHTMLElement* aContent,
 {
   nsCOMPtr<nsILayoutHistoryState> history;
   nsCAutoString key;
-  nsresult rv = GetLayoutHistoryAndKey(aContent, getter_AddRefs(history), key);
+  nsresult rv = GetLayoutHistoryAndKey(aContent, PR_TRUE,
+                                       getter_AddRefs(history), key);
   if (!history) {
     return PR_FALSE;
   }
diff --git a/mozilla/content/html/content/src/nsGenericHTMLElement.h b/mozilla/content/html/content/src/nsGenericHTMLElement.h
index b497be39526..644bff7df19 100644
--- a/mozilla/content/html/content/src/nsGenericHTMLElement.h
+++ b/mozilla/content/html/content/src/nsGenericHTMLElement.h
@@ -527,10 +527,13 @@ public:
    * piece of content.
    *
    * @param aContent the content to generate the key for
+   * @param aRead if true, won't return a layout history state (and won't
+   *              generate a key) if the layout history state is empty.
    * @param aState the history state object (out param)
    * @param aKey the key (out param)
    */
   static nsresult GetLayoutHistoryAndKey(nsGenericHTMLElement* aContent,
+                                         PRBool aRead,
                                          nsILayoutHistoryState** aState,
                                          nsACString& aKey);
   /**
diff --git a/mozilla/layout/base/nsILayoutHistoryState.h b/mozilla/layout/base/nsILayoutHistoryState.h
index 1df07a1da45..52a15dc450a 100644
--- a/mozilla/layout/base/nsILayoutHistoryState.h
+++ b/mozilla/layout/base/nsILayoutHistoryState.h
@@ -50,8 +50,8 @@
 class nsPresState;
 
 #define NS_ILAYOUTHISTORYSTATE_IID \
-{0xe6abfb7c, 0x6624, 0x4b4d, \
-{0x9d, 0xfe, 0xea, 0x62, 0xae, 0xfe, 0x03, 0x31}}
+{ 0x99003f0f, 0x7ade, 0x44a1, \
+ { 0x81, 0x74, 0xe3, 0x6a, 0xa5, 0xbb, 0x6b, 0x10 } }
 
 class nsILayoutHistoryState : public nsISupports {
  public: 
@@ -74,6 +74,11 @@ class nsILayoutHistoryState : public nsISupports {
    * Remove the state object for |aKey|.
    */
   NS_IMETHOD RemoveState(const nsCString& aKey) = 0;
+
+  /**
+   * Check whether this history has any states in it
+   */
+  NS_IMETHOD_(PRBool) HasStates() const = 0;
 };
 
 NS_DEFINE_STATIC_IID_ACCESSOR(nsILayoutHistoryState,
diff --git a/mozilla/layout/base/nsLayoutHistoryState.cpp b/mozilla/layout/base/nsLayoutHistoryState.cpp
index 61ec23edd12..61403f1a922 100644
--- a/mozilla/layout/base/nsLayoutHistoryState.cpp
+++ b/mozilla/layout/base/nsLayoutHistoryState.cpp
@@ -58,6 +58,7 @@ public:
   NS_IMETHOD AddState(const nsCString& aKey, nsPresState* aState);
   NS_IMETHOD GetState(const nsCString& aKey, nsPresState** aState);
   NS_IMETHOD RemoveState(const nsCString& aKey);
+  NS_IMETHOD_(PRBool) HasStates() const;
 
 
 private:
@@ -116,3 +117,9 @@ nsLayoutHistoryState::RemoveState(const nsCString& aKey)
   mStates.Remove(aKey);
   return NS_OK;
 }
+
+NS_IMETHODIMP_(PRBool)
+nsLayoutHistoryState::HasStates() const
+{
+  return mStates.Count() != 0;
+}