Re-land: ui: Add GLImage unit test framework.

ui/gl/gl_api_unittest.cc

 // 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.
 
 #include "base/command_line.h"
 #include "base/memory/scoped_ptr.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/gl/gl_context.h"
 #include "ui/gl/gl_gl_api_implementation.h"
 #include "ui/gl/gl_implementation.h"
@@ skipping 22 matching lines @@
 };
 
 class GLApiTest : public testing::Test {
  public:
   void SetUp() override {
     fake_extension_string_ = "";
     fake_version_string_ = "";
     num_fake_extension_strings_ = 0;
     fake_extension_strings_ = nullptr;
 
+    DCHECK(!g_current_gl_context_tls);
     g_current_gl_context_tls = new base::ThreadLocalPointer<GLApi>;
 
     SetGLGetProcAddressProc(
         static_cast<GLGetProcAddressProc>(&FakeGLGetProcAddress));
   }
 
   static void* GL_BINDING_CALL FakeGLGetProcAddress(const char *proc) {
     return reinterpret_cast<void*>(0x1);
   }
 
   void TearDown() override {
     api_.reset(nullptr);
     delete g_current_gl_context_tls;
+    g_current_gl_context_tls = nullptr;
 
     SetGLImplementation(kGLImplementationNone);
     fake_extension_string_ = "";
     fake_version_string_ = "";
     num_fake_extension_strings_ = 0;
     fake_extension_strings_ = nullptr;
   }
 
   void InitializeAPI(base::CommandLine* command_line) {
     api_.reset(new RealGLApi());
@@ skipping 139 matching lines @@
                                  kFakeDisabledExtensions);
   InitializeAPI(&command_line);
 
   EXPECT_EQ(arraysize(kFilteredExtensions), GetNumExtensions());
   for (uint32_t i = 0; i < arraysize(kFilteredExtensions); ++i) {
     EXPECT_STREQ(kFilteredExtensions[i], GetExtensioni(i));
   }
 }
 
 }  // namespace gfx