[chromecast] Add ExecuteJavaScript method for CastWebContents

Adds a ExecuteJavaScript method for CastWebContents to run script on the
main frame's context.
The method would accept string script and a OnceCallback that is used to
receive a result later.

Bug: Internal b/150822089
Test: cast_web_contents_browsertest
Change-Id: I15e43f62036907e667278f954d06b0bb035c59cc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2123639
Commit-Queue: Jiawei Li <lijiawei@chromium.org>
Reviewed-by: Sean Topping <seantopping@chromium.org>
Reviewed-by: Yuchen Liu <yucliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#754163}

chromecast/browser/cast_web_contents.h

@@ -371,6 +371,16 @@ class CastWebContents {
       const std::string& data,
       std::vector<blink::WebMessagePort> ports) = 0;
 
+  // Executes a string of JavaScript in the main frame's context.
+  // This is no-op if the main frame is not available.
+  // Pass in a callback to receive a result when it is available.
+  // If there is no need to receive the result, pass in a
+  // default-constructed callback. If provided, the callback
+  // will be invoked on the UI thread.
+  virtual void ExecuteJavaScript(
+      const base::string16& javascript,
+      base::OnceCallback<void(base::Value)> callback) = 0;
+
   // ===========================================================================
   // Utility Methods
   // ===========================================================================

chromecast/browser/cast_web_contents_browsertest.cc

@@ -1143,6 +1143,59 @@ IN_PROC_BROWSER_TEST_F(CastWebContentsBrowserTest,
   }
 }
 
+IN_PROC_BROWSER_TEST_F(CastWebContentsBrowserTest, ExecuteJavaScript) {
+  // Start test server for hosting test HTML pages.
+  embedded_test_server()->ServeFilesFromSourceDirectory(GetTestDataPath());
+  StartTestServer();
+  auto run_loop = std::make_unique<base::RunLoop>();
+  auto quit_closure = [&run_loop]() {
+    if (run_loop->running()) {
+      run_loop->QuitWhenIdle();
+    }
+  };
+
+  // ===========================================================================
+  // Test: Set a value using ExecuteJavaScript with empty callback, and then use
+  // ExecuteJavaScript with callback to retrieve that value.
+  // ===========================================================================
+  constexpr char kSoyMilkJsonStringLiteral[] = "\"SoyMilk\"";
+
+  // Load page with title "hello":
+  GURL gurl{embedded_test_server()->GetURL("/title1.html")};
+  {
+    InSequence seq;
+    EXPECT_CALL(
+        mock_cast_wc_observer_,
+        OnPageStateChanged(CheckPageState(
+            cast_web_contents_.get(), CastWebContents::PageState::LOADING)));
+    EXPECT_CALL(
+        mock_cast_wc_observer_,
+        OnPageStateChanged(CheckPageState(cast_web_contents_.get(),
+                                          CastWebContents::PageState::LOADED)))
+        .WillOnce(InvokeWithoutArgs(quit_closure));
+  }
+  cast_web_contents_->LoadUrl(gurl);
+  run_loop->Run();
+
+  // Execute with empty callback.
+  cast_web_contents_->ExecuteJavaScript(
+      base::UTF8ToUTF16(
+          base::StringPrintf("const the_var = %s;", kSoyMilkJsonStringLiteral)),
+      base::DoNothing());
+
+  // Execute a script snippet to return the variable's value.
+  base::RunLoop run_loop2;
+  cast_web_contents_->ExecuteJavaScript(
+      base::UTF8ToUTF16("the_var;"),
+      base::BindLambdaForTesting([&](base::Value result_value) {
+        std::string result_json;
+        ASSERT_TRUE(base::JSONWriter::Write(result_value, &result_json));
+        EXPECT_EQ(result_json, kSoyMilkJsonStringLiteral);
+        run_loop2.Quit();
+      }));
+  run_loop2.Run();
+}
+
 }  // namespace chromecast
 
 #endif  // CHROMECAST_BROWSER_CAST_WEB_CONTENTS_BROWSERTEST_H_

chromecast/browser/cast_web_contents_impl.cc

@@ -104,8 +104,7 @@ CastWebContents* CastWebContents::FromWebContents(
   return *it;
 }
 
-void CastWebContentsImpl::RenderProcessReady(
-    content::RenderProcessHost* host) {
+void CastWebContentsImpl::RenderProcessReady(content::RenderProcessHost* host) {
   DCHECK(host->IsReady());
   const base::Process& process = host->GetProcess();
   for (auto& observer : observer_list_) {
@@ -431,6 +430,18 @@ void CastWebContentsImpl::PostMessageToMainFrame(
       std::move(ports));
 }
 
+void CastWebContentsImpl::ExecuteJavaScript(
+    const base::string16& javascript,
+    base::OnceCallback<void(base::Value)> callback) {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+  if (!web_contents_ || closing_ || !main_frame_loaded_ ||
+      !web_contents_->GetMainFrame())
+    return;
+
+  web_contents_->GetMainFrame()->ExecuteJavaScript(javascript,
+                                                   std::move(callback));
+}
+
 void CastWebContentsImpl::AddObserver(CastWebContents::Observer* observer) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK(observer);

chromecast/browser/cast_web_contents_impl.h

@@ -82,6 +82,9 @@ class CastWebContentsImpl : public CastWebContents,
       const std::string& target_origin,
       const std::string& data,
       std::vector<blink::WebMessagePort> ports) override;
+  void ExecuteJavaScript(
+      const base::string16& javascript,
+      base::OnceCallback<void(base::Value)> callback) override;
   void AddObserver(Observer* observer) override;
   void RemoveObserver(Observer* observer) override;
   bool is_websql_enabled() override;