[headless] Fix screenshots with gpu enabled.

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 18b4295c2b94e42e8db687ebd4652e6a5750af99..03097ca13d1269205bde14bbd2ce1af7e546e543 100644
--- a/headless/lib/headless_web_contents_browsertest.cc
+++ b/headless/lib/headless_web_contents_browsertest.cc
@@ -6,8 +6,10 @@
 #include <string>
 #include <vector>
 
+#include "base/base64.h"
 #include "content/public/test/browser_test.h"
 #include "headless/public/devtools/domains/page.h"
+#include "headless/public/devtools/domains/runtime.h"
 #include "headless/public/devtools/domains/security.h"
 #include "headless/public/headless_browser.h"
 #include "headless/public/headless_devtools_client.h"
@@ -15,6 +17,9 @@
 #include "headless/test/headless_browser_test.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/skia/include/core/SkBitmap.h"
+#include "third_party/skia/include/core/SkColor.h"
+#include "ui/gfx/codec/png_codec.h"
 #include "ui/gfx/geometry/size.h"
 #include "url/gurl.h"
 
@@ -56,10 +61,41 @@ IN_PROC_BROWSER_TEST_F(HeadlessWebContentsTest, WindowOpen) {
             browser_context->GetAllWebContents().size());
 }
 
+namespace {
+bool DecodePNG(std::string base64_data, SkBitmap* bitmap) {
+  std::string png_data;
+  if (!base::Base64Decode(base64_data, &png_data))
+    return false;
+  return gfx::PNGCodec::Decode(
+      reinterpret_cast<unsigned const char*>(png_data.data()), png_data.size(),
+      bitmap);
+}
+}  // namespace
+
+// Parameter specifies whether --disable-gpu should be used.
 class HeadlessWebContentsScreenshotTest
-    : public HeadlessAsyncDevTooledBrowserTest {
+    : public HeadlessAsyncDevTooledBrowserTest,
+      public ::testing::WithParamInterface<bool> {
  public:
+  void SetUp() override {
+    EnablePixelOutput();
+    if (GetParam())
+      UseSoftwareCompositing();
+    HeadlessAsyncDevTooledBrowserTest::SetUp();
+  }
+
   void RunDevTooledTest() override {
+    std::unique_ptr<runtime::EvaluateParams> params =
+        runtime::EvaluateParams::Builder()
+            .SetExpression("document.body.style.background = '#0000ff'")
+            .Build();
+    devtools_client_->GetRuntime()->Evaluate(
+        std::move(params),
+        base::Bind(&HeadlessWebContentsScreenshotTest::OnPageSetupCompleted,
+                   base::Unretained(this)));
+  }
+
+  void OnPageSetupCompleted(std::unique_ptr<runtime::EvaluateResult> result) {
     devtools_client_->GetPage()->GetExperimental()->CaptureScreenshot(
         page::CaptureScreenshotParams::Builder().Build(),
         base::Bind(&HeadlessWebContentsScreenshotTest::OnScreenshotCaptured,
@@ -68,12 +104,26 @@ class HeadlessWebContentsScreenshotTest
 
   void OnScreenshotCaptured(
       std::unique_ptr<page::CaptureScreenshotResult> result) {
-    EXPECT_LT(0U, result->GetData().length());
+    std::string base64 = result->GetData();
+    EXPECT_LT(0U, base64.length());
+    SkBitmap result_bitmap;
+    EXPECT_TRUE(DecodePNG(base64, &result_bitmap));
+
+    EXPECT_EQ(800, result_bitmap.width());
+    EXPECT_EQ(600, result_bitmap.height());
+    SkColor actual_color = result_bitmap.getColor(400, 300);
+    SkColor expected_color = SkColorSetRGB(0x00, 0x00, 0xff);
+    EXPECT_EQ(expected_color, actual_color);
     FinishAsynchronousTest();
   }
 };
 
-HEADLESS_ASYNC_DEVTOOLED_TEST_F(HeadlessWebContentsScreenshotTest);
+HEADLESS_ASYNC_DEVTOOLED_TEST_P(HeadlessWebContentsScreenshotTest);
+
+// Instantiate test case for both software and gpu compositing modes.
+INSTANTIATE_TEST_CASE_P(HeadlessWebContentsScreenshotTests,
+                        HeadlessWebContentsScreenshotTest,
+                        ::testing::Bool());
 
 class HeadlessWebContentsSecurityTest
     : public HeadlessAsyncDevTooledBrowserTest,