Reenable IOSurface Canvas2D. Disable new trace tests.

content/test/gpu/gpu_tests/trace_test_expectations.py

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 from gpu_tests.gpu_test_expectations import GpuTestExpectations
 
 # See the GpuTestExpectations class for documentation.
 
 class TraceTestExpectations(GpuTestExpectations):
   def SetExpectations(self):
     # Sample Usage:
     # self.Fail('TraceTest.Canvas2DRedBox',
     #     ['mac', 'amd', ('nvidia', 0x1234)], bug=123)
-    pass
+
+    # Skip some stories as a temporary debugging measure.
+    # https://crbug.com/595754.
+    self.Skip('trace_test.IOSurface2DCanvasWebGL', ['mac'], bug=595754)
+    self.Skip('trace_test.2DCanvasWebGL', bug=595754)
 
 
 class DeviceTraceTestExpectations(GpuTestExpectations):
   def SetExpectations(self):
     # Device traces are not supported on all machines.
     self.Skip('*')