Force isolation of clip and matrix within layer

bug:17379260

Unclipped save layers need to isolate their clips and matrices
so that the save time readout of background content matches clip and
position with the restore/compose step.

Change-Id: I2de474cda76e960d080852f1716d6ddfa8a512d4
diff --git a/libs/hwui/OpenGLRenderer.cpp b/libs/hwui/OpenGLRenderer.cpp
index 31cc1c8..74f36ab 100755
--- a/libs/hwui/OpenGLRenderer.cpp
+++ b/libs/hwui/OpenGLRenderer.cpp
@@ -638,6 +638,9 @@
 
 int OpenGLRenderer::saveLayer(float left, float top, float right, float bottom,
         const SkPaint* paint, int flags, const SkPath* convexMask) {
+    // force matrix/clip isolation for layer
+    flags |= SkCanvas::kClip_SaveFlag | SkCanvas::kMatrix_SaveFlag;
+
     const int count = saveSnapshot(flags);
 
     if (!currentSnapshot()->isIgnored()) {