Fix rendering artifacts in pull-saveLayers-forward mode

src/gpu/SkGpuDevice.cpp

Index: src/gpu/SkGpuDevice.cpp
===================================================================
--- src/gpu/SkGpuDevice.cpp	(revision 14658)
+++ src/gpu/SkGpuDevice.cpp	(working copy)
@@ -1997,12 +1997,19 @@
         }
     } else {
         // In this case there is no BBH associated with the picture. Pre-render
-        // all the layers
-        // TODO: intersect the bounds of each layer with the clip region to
-        // reduce the number of pre-rendered layers
+        // all the layers that intersect the drawn region
         for (int j = 0; j < gpuData->numSaveLayers(); ++j) {
             const GPUAccelData::SaveLayerInfo& info = gpuData->saveLayerInfo(j);
 
+            SkIRect layerRect = SkIRect::MakeXYWH(info.fOffset.fX,
+                                                  info.fOffset.fY,
+                                                  info.fSize.fWidth,
+                                                  info.fSize.fHeight);
+
+            if (!SkIRect::Intersects(query, layerRect)) {
+                continue;
+            }
+
             // TODO: once this code is more stable unsuitable layers can
             // just be omitted during the optimization stage
             if (!info.fValid ||