Bug 585817. Part 1: Create a single static 1x1 surface in gfxPlatform that can be used to create contexts for text measurement etc. r=vlad

gfx/thebes/gfxPlatform.cpp

@@ -238,6 +238,15 @@ gfxPlatform::Init()
     if (!gPlatform)
         return NS_ERROR_OUT_OF_MEMORY;
 
+    gPlatform->mScreenReferenceSurface =
+      gPlatform->CreateOffscreenSurface(gfxIntSize(1,1),
+                                        gfxASurface::ImageFormatARGB32);
+    if (!gPlatform->mScreenReferenceSurface) {
+      NS_ERROR("Could not initialize mScreenReferenceSurface");
+      Shutdown();
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+
     nsresult rv;
 
 #if defined(XP_MACOSX) || defined(XP_WIN) || defined(ANDROID) // temporary, until this is implemented on others

gfx/thebes/gfxPlatform.h

@@ -339,6 +339,12 @@ public:
 
     virtual void FontsPrefsChanged(nsIPrefBranch *aPrefBranch, const char *aPref);
 
+    /**
+     * Returns a 1x1 surface that can be used to create graphics contexts
+     * for measuring text etc as if they will be rendered to the screen
+     */
+    gfxASurface* ScreenReferenceSurface() { return mScreenReferenceSurface; }
+
 protected:
     gfxPlatform();
     virtual ~gfxPlatform();
@@ -356,8 +362,8 @@ protected:
 private:
     virtual qcms_profile* GetPlatformCMSOutputProfile();
 
+    nsRefPtr<gfxASurface> mScreenReferenceSurface;
     nsTArray<PRUint32> mCJKPrefLangs;
-
     nsCOMPtr<nsIObserver> overrideObserver;
 };