Fix layer blending bug

Cached layers were sometimes retaining an obsolete blending
value, causing artifacts where translucent objects were disappearing
completely. Also, added extra tracing info for DisplayLists.

Issue #6303668 Flickering views during SwipeHelper drag

Change-Id: I66ce158652c4a3ed316040585b40b1744e1fad0c

Author: chethaase

libs/hwui/DisplayListRenderer.cpp

@@ -818,7 +818,10 @@ status_t DisplayList::replay(OpenGLRenderer& renderer, uint32_t width,
         indent[i] = ' ';
     }
     indent[count] = '\0';
-    DISPLAY_LIST_LOGD("%sStart display list (%p, %s)", (char*) indent + 2, this, mName.string());
+    Rect* clipRect = renderer.getClipRect();
+    DISPLAY_LIST_LOGD("%sStart display list (%p, %s), clipRect: %.0f, %.f, %.0f, %.0f",
+            (char*) indent + 2, this, mName.string(), clipRect->left, clipRect->top,
+            clipRect->right, clipRect->bottom);
 #endif
 
     renderer.startMark(mName.string());

libs/hwui/OpenGLRenderer.cpp

@@ -520,6 +520,7 @@ bool OpenGLRenderer::createLayer(sp<Snapshot> snapshot, float left, float top,
     layer->texCoords.set(0.0f, bounds.getHeight() / float(layer->getHeight()),
             bounds.getWidth() / float(layer->getWidth()), 0.0f);
     layer->setColorFilter(mColorFilter);
+    layer->setBlend(true);
 
     // Save the layer in the snapshot
     snapshot->flags |= Snapshot::kFlagIsLayer;
@@ -1058,6 +1059,10 @@ bool OpenGLRenderer::clipRect(float left, float top, float right, float bottom,
     return !mSnapshot->clipRect->isEmpty();
 }
 
+Rect* OpenGLRenderer::getClipRect() {
+    return mSnapshot->clipRect;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // Drawing commands
 ///////////////////////////////////////////////////////////////////////////////

libs/hwui/OpenGLRenderer.h

@@ -101,6 +101,7 @@ class OpenGLRenderer {
     ANDROID_API const Rect& getClipBounds();
     ANDROID_API bool quickReject(float left, float top, float right, float bottom);
     virtual bool clipRect(float left, float top, float right, float bottom, SkRegion::Op op);
+    virtual Rect* getClipRect();
 
     virtual status_t drawDisplayList(DisplayList* displayList, uint32_t width, uint32_t height,
             Rect& dirty, int32_t flags, uint32_t level = 0);