From 98c45828b164d9471f6173be35e9f77251bb672b Mon Sep 17 00:00:00 2001
From: Kartikaya Gupta <kgupta@mozilla.com>
Date: Wed, 12 Mar 2014 15:27:44 -0400
Subject: [PATCH] Bug 981029 - Make ProcessUpdateFrame behave in less magical
 ways. r=botond

Replace the always-true return value, with a FrameMetrics object that
reflects the final metrics put in place. Also remove the side-effect of
assigning mLastRootMetrics and put that in the call sites instead.
---
 dom/ipc/TabChild.cpp | 17 ++++++++---------
 dom/ipc/TabChild.h   |  2 +-
 2 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/dom/ipc/TabChild.cpp b/dom/ipc/TabChild.cpp
index 5de42fef21f..02c9457b44a 100644
--- a/dom/ipc/TabChild.cpp
+++ b/dom/ipc/TabChild.cpp
@@ -661,7 +661,7 @@ TabChild::HandlePossibleViewportChange()
 
   // Force a repaint with these metrics. This, among other things, sets the
   // displayport, so we start with async painting.
-  ProcessUpdateFrame(metrics);
+  mLastRootMetrics = ProcessUpdateFrame(metrics);
 
   if (viewportInfo.IsZoomAllowed() && scrollIdentifiersValid) {
     // If the CSS viewport is narrower than the screen (i.e. width <= device-width)
@@ -1477,7 +1477,8 @@ TabChild::RecvUpdateFrame(const FrameMetrics& aFrameMetrics)
   if (aFrameMetrics.mIsRoot) {
     nsCOMPtr<nsIDOMWindowUtils> utils(GetDOMWindowUtils());
     if (APZCCallbackHelper::HasValidPresShellId(utils, aFrameMetrics)) {
-      return ProcessUpdateFrame(aFrameMetrics);
+      mLastRootMetrics = ProcessUpdateFrame(aFrameMetrics);
+      return true;
     }
   } else {
     // aFrameMetrics.mIsRoot is false, so we are trying to update a subframe.
@@ -1494,7 +1495,8 @@ TabChild::RecvUpdateFrame(const FrameMetrics& aFrameMetrics)
   // We've recieved a message that is out of date and we want to ignore.
   // However we can't reply without painting so we reply by painting the
   // exact same thing as we did before.
-  return ProcessUpdateFrame(mLastRootMetrics);
+  mLastRootMetrics = ProcessUpdateFrame(mLastRootMetrics);
+  return true;
 }
 
 bool
@@ -1505,11 +1507,11 @@ TabChild::RecvAcknowledgeScrollUpdate(const ViewID& aScrollId,
   return true;
 }
 
-bool
+FrameMetrics
 TabChild::ProcessUpdateFrame(const FrameMetrics& aFrameMetrics)
   {
     if (!mGlobal || !mTabChildGlobal) {
-        return true;
+        return aFrameMetrics;
     }
 
     nsCOMPtr<nsIDOMWindowUtils> utils(GetDOMWindowUtils());
@@ -1549,10 +1551,7 @@ TabChild::ProcessUpdateFrame(const FrameMetrics& aFrameMetrics)
     data.AppendLiteral(" }");
 
     DispatchMessageManagerMessage(NS_LITERAL_STRING("Viewport:Change"), data);
-
-    mLastRootMetrics = newMetrics;
-
-    return true;
+    return newMetrics;
 }
 
 bool
diff --git a/dom/ipc/TabChild.h b/dom/ipc/TabChild.h
index 45feab6039f..5e6ba0210fe 100644
--- a/dom/ipc/TabChild.h
+++ b/dom/ipc/TabChild.h
@@ -417,7 +417,7 @@ private:
     bool InitRenderingState();
     void DestroyWindow();
     void SetProcessNameToAppName();
-    bool ProcessUpdateFrame(const mozilla::layers::FrameMetrics& aFrameMetrics);
+    FrameMetrics ProcessUpdateFrame(const FrameMetrics& aFrameMetrics);
 
     // Call RecvShow(nsIntSize(0, 0)) and block future calls to RecvShow().
     void DoFakeShow();