Bug 585817, part -1: Create and expose a scratch DC from gfxWindowsPlatform. r=roc

gfx/thebes/gfxWindowsPlatform.cpp

@@ -198,6 +198,8 @@ gfxWindowsPlatform::gfxWindowsPlatform()
     mUseClearTypeForDownloadableFonts = UNINITIALIZED_VALUE;
     mUseClearTypeAlways = UNINITIALIZED_VALUE;
 
+    mScreenDC = GetDC(NULL);
+
 #ifdef MOZ_FT2_FONTS
     FT_Init_FreeType(&gPlatformFTLibrary);
 #endif
@@ -346,6 +348,7 @@ gfxWindowsPlatform::gfxWindowsPlatform()
 
 gfxWindowsPlatform::~gfxWindowsPlatform()
 {
+    ::ReleaseDC(NULL, mScreenDC);
     // not calling FT_Done_FreeType because cairo may still hold references to
     // these FT_Faces.  See bug 458169.
 #ifdef CAIRO_HAS_D2D_SURFACE

gfx/thebes/gfxWindowsPlatform.h

@@ -148,6 +148,8 @@ public:
     RenderMode GetRenderMode() { return mRenderMode; }
     void SetRenderMode(RenderMode rmode) { mRenderMode = rmode; }
 
+    HDC GetScreenDC() { return mScreenDC; }
+
     nsresult GetFontList(nsIAtom *aLangGroup,
                          const nsACString& aGenericFamily,
                          nsTArray<nsString>& aListOfFonts);
@@ -230,6 +232,7 @@ protected:
 
     PRBool mUseClearTypeForDownloadableFonts;
     PRBool mUseClearTypeAlways;
+    HDC mScreenDC;
 
 private:
     void Init();