Bug 575336 part 1. Make sure to update the size of the current prescontext on style flush, so that media queries do the right thing. r=roc

layout/base/nsPresShell.cpp

@@ -4789,6 +4789,7 @@ PresShell::FlushPendingNotifications(mozFlushType aType)
     // Process pending restyles, since any flush of the presshell wants
     // up-to-date style data.
     if (!mIsDestroying) {
+      mViewManager->FlushDelayedResize(PR_FALSE);
       mPresContext->FlushPendingMediaFeatureValuesChanged();
 
       // Flush any pending update of the user font set, since that could
@@ -4835,7 +4836,7 @@ PresShell::FlushPendingNotifications(mozFlushType aType)
     if (aType >= (mSuppressInterruptibleReflows ? Flush_Layout : Flush_InterruptibleLayout) &&
         !mIsDestroying) {
       mFrameConstructor->RecalcQuotesAndCounters();
-      mViewManager->FlushDelayedResize();
+      mViewManager->FlushDelayedResize(PR_TRUE);
       if (ProcessReflowCommands(aType < Flush_Layout) && mContentToScrollTo) {
         // We didn't get interrupted.  Go ahead and scroll to our content
         DoScrollContentIntoView(mContentToScrollTo, mContentScrollVPosition,

view/public/nsIViewManager.h

@@ -50,8 +50,8 @@ class nsIDeviceContext;
 class nsIViewObserver;
 
 #define NS_IVIEWMANAGER_IID   \
-  { 0x9e924719, 0x3c4b, 0x435b, \
-    { 0xaf, 0x1e, 0x71, 0x52, 0x04, 0x6d, 0xaa, 0x44 } }
+  { 0x35c07b12, 0x5d96, 0x49f9, \
+   { 0x91, 0xa3, 0x2f, 0xad, 0x3e, 0x84, 0x0c, 0x91 } }
 
 class nsIViewManager : public nsISupports
 {
@@ -116,7 +116,7 @@ public:
   /**
    * Do any resizes that are pending.
    */
-  NS_IMETHOD  FlushDelayedResize() = 0;
+  NS_IMETHOD  FlushDelayedResize(PRBool aDoReflow) = 0;
 
   /**
    * Called to force a redrawing of any dirty areas.

view/src/nsViewManager.cpp

@@ -60,6 +60,8 @@
 #include "nsContentUtils.h"
 #include "nsIPluginWidget.h"
 #include "nsXULPopupManager.h"
+#include "nsIPresShell.h"
+#include "nsPresContext.h"
 
 static NS_DEFINE_IID(kRegionCID, NS_REGION_CID);
 
@@ -333,11 +335,19 @@ NS_IMETHODIMP nsViewManager::SetWindowDimensions(nscoord aWidth, nscoord aHeight
   return NS_OK;
 }
 
-NS_IMETHODIMP nsViewManager::FlushDelayedResize()
+NS_IMETHODIMP nsViewManager::FlushDelayedResize(PRBool aDoReflow)
 {
   if (mDelayedResize != nsSize(NSCOORD_NONE, NSCOORD_NONE)) {
-    DoSetWindowDimensions(mDelayedResize.width, mDelayedResize.height);
-    mDelayedResize.SizeTo(NSCOORD_NONE, NSCOORD_NONE);
+    if (aDoReflow) {
+      DoSetWindowDimensions(mDelayedResize.width, mDelayedResize.height);
+      mDelayedResize.SizeTo(NSCOORD_NONE, NSCOORD_NONE);
+    } else if (mObserver) {
+      nsCOMPtr<nsIPresShell> shell = do_QueryInterface(mObserver);
+      nsPresContext* presContext = shell->GetPresContext();
+      if (presContext) {
+        presContext->SetVisibleArea(nsRect(nsPoint(0, 0), mDelayedResize));
+      }
+    }
   }
   return NS_OK;
 }
@@ -842,7 +852,7 @@ NS_IMETHODIMP nsViewManager::DispatchEvent(nsGUIEvent *aEvent,
                       : nsnull) {
             if (vm->mDelayedResize != nsSize(NSCOORD_NONE, NSCOORD_NONE) &&
                 IsViewVisible(vm->mRootView)) {
-              vm->FlushDelayedResize();
+              vm->FlushDelayedResize(PR_TRUE);
 
               // Paint later.
               vm->UpdateView(vm->mRootView, NS_VMREFRESH_NO_SYNC);

view/src/nsViewManager.h

@@ -111,7 +111,7 @@ public:
 
   NS_IMETHOD  GetWindowDimensions(nscoord *width, nscoord *height);
   NS_IMETHOD  SetWindowDimensions(nscoord width, nscoord height);
-  NS_IMETHOD  FlushDelayedResize();
+  NS_IMETHOD  FlushDelayedResize(PRBool aDoReflow);
 
   NS_IMETHOD  Composite(void);