re-enable depth texture gl test

gpu/command_buffer/tests/gl_depth_texture_unittest.cc

Index: gpu/command_buffer/tests/gl_depth_texture_unittest.cc
diff --git a/gpu/command_buffer/tests/gl_depth_texture_unittest.cc b/gpu/command_buffer/tests/gl_depth_texture_unittest.cc
index 3cdddfb85f9230d17d44fed1d01b1d964f1a5962..e7a01aae0c238d67a2d5cb2542cb2694468fd529 100644
--- a/gpu/command_buffer/tests/gl_depth_texture_unittest.cc
+++ b/gpu/command_buffer/tests/gl_depth_texture_unittest.cc
@@ -60,9 +60,7 @@ struct FormatType {
 
 }  // anonymous namespace
 
-// Temporarily marked disabled due to failure on gpu bots.
-// https://code.google.com/p/chromium/issues/detail?id=135229
-TEST_F(DepthTextureTest, DISABLED_RenderTo) {
+TEST_F(DepthTextureTest, RenderTo) {
   if (!GLTestHelper::HasExtension("GL_CHROMIUM_depth_texture")) {
     return;
   }
@@ -189,6 +187,8 @@ TEST_F(DepthTextureTest, DISABLED_RenderTo) {
         if (yy > 0) {
           EXPECT_GT(actual[0], down[0]);
         }
+
+        EXPECT_TRUE(actual[3] == actual[0] || actual[3] == 0xFF);
       }
     }