Fix glop rendering within unclipped saveLayers

bug:19541881

Additionally, clean up GlopBuilders
and rename onGetSnapshot() for clarity

Change-Id: I0303e4cd61eef87cf80af2d968c4aa67193cd008
diff --git a/libs/hwui/OpenGLRenderer.h b/libs/hwui/OpenGLRenderer.h
index ae53313..63a63b8 100755
--- a/libs/hwui/OpenGLRenderer.h
+++ b/libs/hwui/OpenGLRenderer.h
@@ -426,7 +426,7 @@
 
     virtual void onViewportInitialized() override;
     virtual void onSnapshotRestored(const Snapshot& removed, const Snapshot& restored) override;
-    virtual GLuint onGetTargetFbo() const override { return 0; }
+    virtual GLuint getTargetFbo() const override { return 0; }
 
     SkPath* allocPathForFrame() {
         std::unique_ptr<SkPath> path(new SkPath());
@@ -569,7 +569,7 @@
     RenderState& mRenderState;
 
 private:
-    void renderGlop(const Glop& glop);
+    void renderGlop(const Glop& glop, bool clearLayer = true);
 
     /**
      * Discards the content of the framebuffer if supported by the driver.