Add HeadlessFocusClient to fix document.hasFocus() issues.

headless/lib/headless_web_contents_browsertest.cc

Index: headless/lib/headless_web_contents_browsertest.cc
diff --git a/headless/lib/headless_web_contents_browsertest.cc b/headless/lib/headless_web_contents_browsertest.cc
index 693e2dceeaa7ce9a1e380914e119a2923fabe70c..22e387752852b8402d05449dccb1db3ac146e275 100644
--- a/headless/lib/headless_web_contents_browsertest.cc
+++ b/headless/lib/headless_web_contents_browsertest.cc
@@ -61,6 +61,38 @@ IN_PROC_BROWSER_TEST_F(HeadlessWebContentsTest, WindowOpen) {
             browser_context->GetAllWebContents().size());
 }
 
+IN_PROC_BROWSER_TEST_F(HeadlessWebContentsTest, Focus) {
+  EXPECT_TRUE(embedded_test_server()->Start());
+
+  HeadlessBrowserContext* browser_context =
+      browser()->CreateBrowserContextBuilder().Build();
+
+  HeadlessWebContents* web_contents =
+      browser_context->CreateWebContentsBuilder()
+          .SetInitialURL(embedded_test_server()->GetURL("/hello.html"))
+          .Build();
+  EXPECT_TRUE(WaitForLoad(web_contents));
+
+  bool result;
+  EXPECT_TRUE(EvaluateScript(web_contents, "document.hasFocus()")
+                  ->GetResult()
+                  ->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));
+
+  EXPECT_TRUE(EvaluateScript(web_contents, "document.hasFocus()")

[Eric Seckler, 2017/02/22 09:00:04]

nit: Let's add a todo here - focus of two web contents should eventually be
independent of each other (for the purposes of isolation). Then, both
web_contents and web_contents2 should be focused at this point.

(Side note - in that future, we may also want a way to explicitly relinquish
focus of a WebContents.)

[irisu, 2017/02/23 00:02:26]

Done.

+                  ->GetResult()
+                  ->GetValue()
+                  ->GetAsBoolean(&result));
+  EXPECT_FALSE(result);
+}
+
 namespace {
 bool DecodePNG(std::string base64_data, SkBitmap* bitmap) {
   std::string png_data;