[headless] Use individual aura::WindowTreeHosts per WebContents.

headless/lib/headless_web_contents_browsertest.cc

 // Copyright 2016 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 <memory>
 #include <string>
 #include <vector>
 
 #include "base/base64.h"
 #include "content/public/test/browser_test.h"
@@ skipping 68 matching lines @@
                   ->GetValue()
                   ->GetAsBoolean(&result));
   EXPECT_TRUE(result);
 
   HeadlessWebContents* web_contents2 =
       browser_context->CreateWebContentsBuilder()
           .SetInitialURL(embedded_test_server()->GetURL("/hello.html"))
           .Build();
   EXPECT_TRUE(WaitForLoad(web_contents2));
 
-  // TODO(irisu): Focus of two web contents should be independent of the other.
-  // Both web_contents and web_contents2 should be focused at this point.
-  // NOTE(dvallet): Mac headless implementation already does this.
+  // Focus of different WebContents is independent.
   EXPECT_TRUE(EvaluateScript(web_contents, "document.hasFocus()")
                   ->GetResult()
                   ->GetValue()
                   ->GetAsBoolean(&result));
-#if !defined(OS_MACOSX)
-  EXPECT_FALSE(result);
-#else
-  // Mac sets all contents as focused.
   EXPECT_TRUE(result);
-#endif
   EXPECT_TRUE(EvaluateScript(web_contents2, "document.hasFocus()")
                   ->GetResult()
                   ->GetValue()
                   ->GetAsBoolean(&result));
   EXPECT_TRUE(result);
 }
 
 namespace {
 bool DecodePNG(std::string base64_data, SkBitmap* bitmap) {
   std::string png_data;
@@ skipping 75 matching lines @@
     devtools_client_->GetSecurity()->GetExperimental()->Disable(
         security::DisableParams::Builder().Build());
     devtools_client_->GetSecurity()->GetExperimental()->RemoveObserver(this);
     FinishAsynchronousTest();
   }
 };
 
 HEADLESS_ASYNC_DEVTOOLED_TEST_F(HeadlessWebContentsSecurityTest);
 
 }  // namespace headless