Make nsSharable[C]String writable by overriding appropriate methods. Ensure that it doesn't store null buffer handle pointer internally, and override get() on nsXPIDL[C]String for backwards-compatibility. Collapse nsSharedBufferHandle and nsFlexBufferHandle into nsSharedBufferHandle which knows its length but can't have a storage start distinct from its data start. Convert string users who were working around broken nsSharableString::Assign back to using it. b=104663, 100751, 74726 r=jag sr=scc

git-svn-id: svn://10.0.0.236/trunk@109114 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/xpcom/io/nsLocalFileUnix.cpp

@@ -265,8 +265,7 @@ nsLocalFile::InitWithPath(const char *filePath)
     ssize_t len  = strlen(filePath);
     while (filePath[len-1] == '/' && len > 1)
         --len;
-    // XXXldb change to |Assign| rather than |Adopt(ToNewCString|
-    mPath.Adopt(ToNewCString(Substring(filePath, filePath+len)));
+    mPath.Assign(Substring(filePath, filePath+len));
 
     InvalidateCache();
     return NS_OK;
@@ -439,8 +438,8 @@ nsLocalFile::AppendRelativePath(const char *fragment)
     if (*fragment == '/')
         return NS_ERROR_FILE_UNRECOGNIZED_PATH;
 
-    mPath.Adopt(ToNewCString(mPath + NS_LITERAL_CSTRING("/") +
-                             nsDependentCString(fragment)));
+    mPath.Assign(mPath + NS_LITERAL_CSTRING("/") +
+                 nsDependentCString(fragment));
 
     if (!mPath.get())
         return NS_ERROR_OUT_OF_MEMORY;