Fix for out-of-sync scale factor issue

- Set active root window early when creating browsers on startup.
- Send screen info when device scale factor chagned.
- gfx::Screen::GetDisplayNearestWindow should return Primary when the window's root doesn't exist. I missed this condition in  https://chromiumcodereview.appspot.com/10961021

BUG=155201, 152728
TEST=manual: see bug for repro steps

Review URL: https://chromiumcodereview.appspot.com/11066130

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@161758 0039d316-1c4b-4281-b951-d872f2087c98

ash/display/multi_display_manager.cc

@@ -307,7 +307,9 @@ const gfx::Display& MultiDisplayManager::GetDisplayNearestWindow(
     return DisplayController::GetPrimaryDisplay();
   const RootWindow* root = window->GetRootWindow();
   MultiDisplayManager* manager = const_cast<MultiDisplayManager*>(this);
-  return root ? manager->FindDisplayForRootWindow(root) : GetInvalidDisplay();
+  return root ?
+      manager->FindDisplayForRootWindow(root) :
+      DisplayController::GetPrimaryDisplay();
 }
 
 const gfx::Display& MultiDisplayManager::GetDisplayNearestPoint(

chrome/browser/ui/startup/startup_browser_creator_impl.cc

@@ -95,6 +95,8 @@
 
 #if defined(USE_ASH)
 #include "ash/launcher/launcher_types.h"
+#include "ash/shell.h"
+#include "ui/aura/window.h"
 #endif
 
 #if defined(OS_MACOSX)
@@ -796,6 +798,18 @@ Browser* StartupBrowserCreatorImpl::OpenTabsInBrowser(Browser* browser,
 #endif
   }
 
+#if defined(USE_ASH)
+  // Set the browser's root window to be an active root window now so
+  // that that web contents can determine correct scale factor for the
+  // renderer. This is a short term fix for crbug.com/155201.  Without
+  // this, the renderer may use wrong scale factor first, then
+  // switched to the correct scale factor, which can cause race
+  // condition and lead to the results rendered at wrong scale factor.
+  // Long term fix is tracked in crbug.com/15543.
+  ash::Shell::GetInstance()->set_active_root_window(
+      browser->window()->GetNativeWindow()->GetRootWindow());
+#endif
+
   // In kiosk mode, we want to always be fullscreen, so switch to that now.
   if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kKioskMode))
     chrome::ToggleFullscreenMode(browser);

content/browser/renderer_host/render_widget_host_impl.cc

@@ -1101,6 +1101,11 @@ void RenderWidgetHostImpl::NotifyScreenInfoChanged() {
 }
 
 void RenderWidgetHostImpl::SetDeviceScaleFactor(float scale) {
+  // Send secreen info as well because JavaScript API |window.open|
+  // uses screen info to determine the scale factor (crbug.com/155201).
+  // TODO(oshima|thakis): Consolidate SetDeviceScaleFactor and
+  // ScreenInfoChanged. crbug.com/155213.
+  NotifyScreenInfoChanged();
   Send(new ViewMsg_SetDeviceScaleFactor(GetRoutingID(), scale));
 }