Add WebviewClient back navigation support

Allows user to test go back functionality.

Bug: 1011977
Test: Run client, use back command.
Change-Id: Ib07e48dd9e07211a9b2b8cf2199d9bc65e4df98d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2142571
Commit-Queue: Shawn Gallea <sagallea@google.com>
Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757908}

chromecast/browser/webview/client/webview.cc

@@ -26,6 +26,7 @@ namespace {
 
 constexpr int kGrpcMaxReconnectBackoffMs = 1000;
 
+constexpr char kBackCommand[] = "back";
 constexpr char kCreateCommand[] = "create";
 constexpr char kDestroyCommand[] = "destroy";
 constexpr char kListCommand[] = "list";
@@ -306,6 +307,8 @@ void WebviewClient::InputCallback() {
     SendResizeRequest(tokens);
   else if (tokens[1] == kPositionCommand)
     SetPosition(tokens);
+  else if (tokens[1] == kBackCommand)
+    SendBackRequest(tokens);
 
   std::cout << "Enter command: ";
   std::cout.flush();
@@ -357,6 +360,22 @@ void WebviewClient::SchedulePaint() {
       FROM_HERE, base::BindOnce(&WebviewClient::Paint, base::Unretained(this)));
 }
 
+void WebviewClient::SendBackRequest(const std::vector<std::string>& tokens) {
+  int id;
+  if (tokens.size() != 2 || !base::StringToInt(tokens[0], &id) ||
+      webviews_.find(id) == webviews_.end()) {
+    LOG(ERROR) << "Usage: [ID] back";
+    return;
+  }
+
+  const auto& webview = webviews_[id];
+  WebviewRequest back_request;
+  back_request.mutable_go_back();
+  if (!webview->client->Write(back_request)) {
+    LOG(ERROR) << ("Back request send failed");
+  }
+}
+
 void WebviewClient::SendNavigationRequest(
     const std::vector<std::string>& tokens) {
   int id;

chromecast/browser/webview/client/webview.h

@@ -81,6 +81,7 @@ class WebviewClient : public exo::wayland::clients::ClientBase {
   void InputCallback();
   void ListActiveWebviews();
   void Paint();
+  void SendBackRequest(const std::vector<std::string>& tokens);
   void SendNavigationRequest(const std::vector<std::string>& tokens);
   void SendResizeRequest(const std::vector<std::string>& tokens);
   void SendTouchInput(const Webview* webview,