aura: Clean up compositor initialization/destruction.

content/browser/gpu/gpu_pixel_browsertest.cc

Index: content/browser/gpu/gpu_pixel_browsertest.cc
diff --git a/content/browser/gpu/gpu_pixel_browsertest.cc b/content/browser/gpu/gpu_pixel_browsertest.cc
index dc0b91f4ce9315221c98289d3a61a278c8ae9065..5909321377f9d05d5817e3ba46c0a0e5015b60b6 100644
--- a/content/browser/gpu/gpu_pixel_browsertest.cc
+++ b/content/browser/gpu/gpu_pixel_browsertest.cc
@@ -24,7 +24,6 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkColor.h"
-#include "ui/compositor/compositor_setup.h"
 #include "ui/gfx/codec/png_codec.h"
 #include "ui/gfx/size.h"
 #include "ui/gl/gl_switches.h"
@@ -106,6 +105,13 @@ class GpuPixelBrowserTest : public ContentBrowserTest {
         ref_img_option_(kReferenceImageNone) {
   }
 
+  virtual void SetUp() {
+    // We expect real pixel output for these tests.
+    UseRealGLContexts();
+
+    ContentBrowserTest::SetUp();
+  }
+
   virtual void SetUpCommandLine(CommandLine* command_line) OVERRIDE {
     command_line->AppendSwitchASCII(switches::kTestGLLib,
                                     "libllvmpipe.so");
@@ -150,8 +156,6 @@ class GpuPixelBrowserTest : public ContentBrowserTest {
       ReplaceFirstSubstringAfterOffset(
           &test_name_, 0, test_status_prefixes[i], std::string());
     }
-
-    ui::DisableTestCompositor();
   }
 
   // If the existing ref image was saved from an revision older than the