From daa8e38158e62d23af8c66b7b8c4b6288d7a9718 Mon Sep 17 00:00:00 2001
From: Wei-Cheng Pan <wpan@mozilla.com>
Date: Wed, 20 Apr 2016 11:41:42 +0800
Subject: [PATCH] Bug 1259641 - Do not force reflow for all tabs when size mode
 changed. r=smaug

MozReview-Commit-ID: GoTCM60Hmlf

--HG--
extra : transplant_source : S%88%AD%A3%99%9Bk%D3%E4U%0302%82%87o3%28%FFK
---
 dom/ipc/TabChild.cpp             | 6 ++++--
 layout/style/nsMediaFeatures.cpp | 3 +++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/dom/ipc/TabChild.cpp b/dom/ipc/TabChild.cpp
index 5eb5d2f26acb..7c74a82c311b 100644
--- a/dom/ipc/TabChild.cpp
+++ b/dom/ipc/TabChild.cpp
@@ -1655,13 +1655,15 @@ bool
 TabChild::RecvSizeModeChanged(const nsSizeMode& aSizeMode)
 {
   mPuppetWidget->SetSizeMode(aSizeMode);
+  if (!mPuppetWidget->IsVisible()) {
+    return true;
+  }
   nsCOMPtr<nsIDocument> document(GetDocument());
   nsCOMPtr<nsIPresShell> presShell = document->GetShell();
   if (presShell) {
     nsPresContext* presContext = presShell->GetPresContext();
     if (presContext) {
-      presContext->MediaFeatureValuesChangedAllDocuments(eRestyle_Subtree,
-                                                         NS_STYLE_HINT_REFLOW);
+      presContext->SizeModeChanged(aSizeMode);
     }
   }
   return true;
diff --git a/layout/style/nsMediaFeatures.cpp b/layout/style/nsMediaFeatures.cpp
index 0bd1b0cfefe5..075e1b251966 100644
--- a/layout/style/nsMediaFeatures.cpp
+++ b/layout/style/nsMediaFeatures.cpp
@@ -328,6 +328,9 @@ GetDisplayMode(nsPresContext* aPresContext, const nsMediaFeature*,
   baseWindow->GetMainWidget(getter_AddRefs(mainWidget));
   int32_t displayMode;
   nsSizeMode mode = mainWidget ? mainWidget->SizeMode() : nsSizeMode_Normal;
+  // Background tabs are always in 'browser' mode for now.
+  // If new modes are supported, please ensure not cause the regression in
+  // Bug 1259641.
   switch (mode) {
     case nsSizeMode_Fullscreen:
       displayMode = NS_STYLE_DISPLAY_MODE_FULLSCREEN;