Fix GC issue, fix local shader transformations.

Change-Id: I208bdf89815dcd18dcadd43df932a77362918435
diff --git a/libs/hwui/SkiaShader.cpp b/libs/hwui/SkiaShader.cpp
index 3569d6a..c7a01b1 100644
--- a/libs/hwui/SkiaShader.cpp
+++ b/libs/hwui/SkiaShader.cpp
@@ -164,7 +164,8 @@
     Rect start(mBounds[0], mBounds[1], mBounds[2], mBounds[3]);
     if (mMatrix) {
         mat4 shaderMatrix(*mMatrix);
-        shaderMatrix.mapRect(start);
+        shaderMatrix.mapPoint(start.left, start.top);
+        shaderMatrix.mapPoint(start.right, start.bottom);
     }
     snapshot.transform.mapRect(start);