headless: Implement screenshot capturing

headless/test/headless_browser_test.cc

Index: headless/test/headless_browser_test.cc
diff --git a/headless/test/headless_browser_test.cc b/headless/test/headless_browser_test.cc
index d308fbead5842407acbc9488a97a1262e48dcc4c..2b6ec614f19eed1cbc6b89268b58e427c21ba19c 100644
--- a/headless/test/headless_browser_test.cc
+++ b/headless/test/headless_browser_test.cc
@@ -19,6 +19,8 @@
 #include "headless/public/headless_devtools_client.h"
 #include "headless/public/headless_devtools_target.h"
 #include "headless/public/headless_web_contents.h"
+#include "ui/gfx/geometry/size.h"
+#include "url/gurl.h"
 
 namespace headless {
 namespace {
@@ -173,4 +175,29 @@ void HeadlessBrowserTest::FinishAsynchronousTest() {
   run_loop_->Quit();
 }
 
+HeadlessAsyncDevTooledBrowserTest::HeadlessAsyncDevTooledBrowserTest()
+    : web_contents_(nullptr),
+      devtools_client_(HeadlessDevToolsClient::Create()) {}
+
+HeadlessAsyncDevTooledBrowserTest::~HeadlessAsyncDevTooledBrowserTest() {}
+
+void HeadlessAsyncDevTooledBrowserTest::DevToolsTargetReady() {
+  EXPECT_TRUE(web_contents_->GetDevToolsTarget());
+  web_contents_->GetDevToolsTarget()->AttachClient(devtools_client_.get());
+  RunDevTooledTest();
+}
+
+void HeadlessAsyncDevTooledBrowserTest::RunTest() {
+  web_contents_ =
+      browser()->CreateWebContents(GURL("about:blank"), gfx::Size(800, 600));
+  web_contents_->AddObserver(this);
+
+  RunAsynchronousTest();
+
+  web_contents_->GetDevToolsTarget()->DetachClient(devtools_client_.get());
+  web_contents_->RemoveObserver(this);
+  web_contents_->Close();
+  web_contents_ = nullptr;
+}
+
 }  // namespace headless