Don't increment the paint's generation ID when drawing bitmaps

When the renderer draws a bitmap as part of a display list with an
alpha < 1.0f, the paint is temporarily modified to alter the opacity
of the bitmap. This has the side effect of increasing the paint's
generation ID counter which can break paint caching.

Change-Id: I5055d059ad1639829fa50af3d946e296c4dab877
diff --git a/libs/hwui/OpenGLRenderer.h b/libs/hwui/OpenGLRenderer.h
index 80f2081..9144a33 100644
--- a/libs/hwui/OpenGLRenderer.h
+++ b/libs/hwui/OpenGLRenderer.h
@@ -259,7 +259,7 @@
     virtual void resetPaintFilter();
     virtual void setupPaintFilter(int clearBits, int setBits);
 
-    SkPaint* filterPaint(SkPaint* paint);
+    SkPaint* filterPaint(SkPaint* paint, bool alwaysCopy = false);
 
     bool disallowDeferral() {
         // returns true if the OpenGLRenderer's state can be completely represented by