Bug 1477898 - Make AutoRestoreEditorState not call EditorBase::SetFlags() since the virtual call cost appears in profile r=m_kato

Unfortunately, EditorBase::SetFlags() is virtual call even though
AutoRestoreEditorState always works only with TextEditor (the method is
overridden only by HTMLEditor).  And AutoRestoreEditorState is a hot path
when <input>.value or <textarea>.value is set a lot.

Fortunately, EditorBase::Flags() can be an inline method.  So, we can make
both constructor and destructor of the class check if it'll change flags
actually.

Additionally, this patch fixes nsTextEditorState::PrepareEditor() too.

MozReview-Commit-ID: 7S4hLRRrbfB

--HG--
extra : rebase_source : 3c3e7438cd7e6c9853e5cf876277d7459b86c343

dom/html/nsTextEditorState.cpp

@@ -50,6 +50,15 @@
 using namespace mozilla;
 using namespace mozilla::dom;
 
+inline nsresult
+SetEditorFlagsIfNecessary(EditorBase& aEditorBase, uint32_t aFlags)
+{
+  if (aEditorBase.Flags() == aFlags) {
+    return NS_OK;
+  }
+  return aEditorBase.SetFlags(aFlags);
+}
+
 class MOZ_STACK_CLASS ValueSetter
 {
 public:
@@ -139,19 +148,24 @@ public:
     MOZ_GUARD_OBJECT_NOTIFIER_INIT;
     MOZ_ASSERT(mTextEditor);
 
+    // EditorBase::SetFlags() is a virtual method.  Even though it does nothing
+    // if new flags and current flags are same, the calling cost causes
+    // appearing the method in profile.  So, this class should check if it's
+    // necessary to call.
     uint32_t flags = mSavedFlags;
     flags &= ~(nsIPlaintextEditor::eEditorDisabledMask);
     flags &= ~(nsIPlaintextEditor::eEditorReadonlyMask);
     flags |= nsIPlaintextEditor::eEditorDontEchoPassword;
-    mTextEditor->SetFlags(flags);
-
+    if (mSavedFlags != flags) {
+      mTextEditor->SetFlags(flags);
+    }
     mTextEditor->SetMaxTextLength(-1);
   }
 
   ~AutoRestoreEditorState()
   {
      mTextEditor->SetMaxTextLength(mSavedMaxLength);
-     mTextEditor->SetFlags(mSavedFlags);
+     SetEditorFlagsIfNecessary(*mTextEditor, mSavedFlags);
   }
 
 private:
@@ -1482,7 +1496,7 @@ nsTextEditorState::PrepareEditor(const nsAString *aValue)
       mSelCon->SetDisplaySelection(nsISelectionController::SELECTION_OFF);
     }
 
-    newTextEditor->SetFlags(editorFlags);
+    SetEditorFlagsIfNecessary(*newTextEditor, editorFlags);
   }
 
   if (shouldInitializeEditor) {
@@ -1496,8 +1510,10 @@ nsTextEditorState::PrepareEditor(const nsAString *aValue)
   // editor for us.
 
   if (!defaultValue.IsEmpty()) {
-    rv = newTextEditor->SetFlags(editorFlags);
-    NS_ENSURE_SUCCESS(rv, rv);
+    rv = SetEditorFlagsIfNecessary(*newTextEditor, editorFlags);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
 
     // Now call SetValue() which will make the necessary editor calls to set
     // the default value.  Make sure to turn off undo before setting the default
@@ -1509,8 +1525,10 @@ nsTextEditorState::PrepareEditor(const nsAString *aValue)
     NS_ENSURE_TRUE(success, NS_ERROR_OUT_OF_MEMORY);
 
     // Now restore the original editor flags.
-    rv = newTextEditor->SetFlags(editorFlags);
-    NS_ENSURE_SUCCESS(rv, rv);
+    rv = SetEditorFlagsIfNecessary(*newTextEditor, editorFlags);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
   }
 
   if (IsPasswordTextControl()) {