Add gpu implementation of OverdrawXfermode

gyp/tests.gypi

 # Copyright 2015 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 # Common gypi for unit tests.
 {
   'include_dirs': [
     '../include/private',
     '../src/codec',
     '../src/core',
@@ skipping 39 matching lines @@
   ],
   'sources': [
     '../tests/Test.h',
     '<!@(python find.py ../tests "*.c*")',
     '../src/utils/debugger/SkDrawCommand.h',
     '../src/utils/debugger/SkDrawCommand.cpp',
     '../src/utils/debugger/SkDebugCanvas.h',
     '../src/utils/debugger/SkDebugCanvas.cpp',
     '../src/utils/debugger/SkObjectParser.h',
     '../src/utils/debugger/SkObjectParser.cpp',
+    '../src/utils/debugger/SkOverdrawMode.h',
+    '../src/utils/debugger/SkOverdrawMode.cpp',
   ],
   'sources!': [
     '../tests/SkpSkGrTest.cpp',
     '../tests/skia_test.cpp',
     '../tests/PathOpsAngleIdeas.cpp',
     '../tests/PathOpsBattles.cpp',
     '../tests/PathOpsCubicLineIntersectionIdeas.cpp',
     '../tests/PathOpsDebug.cpp',
     '../tests/PathOpsOpLoopThreadedTest.cpp',
     '../tests/PathOpsSkpClipTest.cpp',
   ],
 }