headless: Implement screenshot capturing

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 30faee5e65ef2edf70551c8d55a642af152f4333..5cff88c0441b2529962893f61341be2272bb62e3 100644
--- a/headless/lib/headless_web_contents_browsertest.cc
+++ b/headless/lib/headless_web_contents_browsertest.cc
@@ -3,9 +3,13 @@
 // found in the LICENSE file.
 
 #include <memory>
+#include <string>
+#include <vector>
 
 #include "content/public/test/browser_test.h"
+#include "headless/public/domains/page.h"
 #include "headless/public/headless_browser.h"
+#include "headless/public/headless_devtools_client.h"
 #include "headless/public/headless_web_contents.h"
 #include "headless/test/headless_browser_test.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -18,6 +22,7 @@ class HeadlessWebContentsTest : public HeadlessBrowserTest {};
 
 IN_PROC_BROWSER_TEST_F(HeadlessWebContentsTest, Navigation) {
   EXPECT_TRUE(embedded_test_server()->Start());
+
   HeadlessWebContents* web_contents = browser()->CreateWebContents(
       embedded_test_server()->GetURL("/hello.html"), gfx::Size(800, 600));
   EXPECT_TRUE(WaitForLoad(web_contents));
@@ -42,4 +47,23 @@ IN_PROC_BROWSER_TEST_F(HeadlessWebContentsTest, WindowOpen) {
   EXPECT_EQ(static_cast<size_t>(2), all_web_contents.size());
 }
 
+class HeadlessWebContentsScreenshotTest
+    : public HeadlessAsyncDevTooledBrowserTest {
+ public:
+  void RunDevTooledTest() override {
+    devtools_client_->GetPage()->GetExperimental()->CaptureScreenshot(
+        page::CaptureScreenshotParams::Builder().Build(),
+        base::Bind(&HeadlessWebContentsScreenshotTest::OnScreenshotCaptured,
+                   base::Unretained(this)));
+  }
+
+  void OnScreenshotCaptured(
+      std::unique_ptr<page::CaptureScreenshotResult> result) {
+    EXPECT_LT(0U, result->GetData().length());
+    FinishAsynchronousTest();
+  }
+};
+
+HEADLESS_ASYNC_DEVTOOLED_TEST_F(HeadlessWebContentsScreenshotTest);
+
 }  // namespace headless