Upstreaming changes from android.

- fix compile warnings in the GPU code
- upstream android specific code (ifdef protected)
- fail gracefully when a custom allocator fails



git-svn-id: http://skia.googlecode.com/svn/trunk@936 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/effects/SkPorterDuff.h b/include/effects/SkPorterDuff.h
index 6f4ac20..54f81ea 100644
--- a/include/effects/SkPorterDuff.h
+++ b/include/effects/SkPorterDuff.h
@@ -52,6 +52,9 @@
         kMultiply_Mode, //!< [Sa * Da, Sc * Dc]
         kScreen_Mode,   //!< [Sa + Da - Sa * Da, Sc + Dc - Sc * Dc]
         kAdd_Mode,      //!< Saturate(S + D)
+#ifdef ANDROID
+        kOverlay_Mode,
+#endif
 
         kModeCount
     };