[DevTools] Implement Page.canEmulate capability.

BUG=none

Review URL: https://codereview.chromium.org/501153006

Cr-Commit-Position: refs/heads/master@{#292374}

content/browser/devtools/renderer_overrides_handler.cc

@@ -40,6 +40,7 @@
 #include "content/public/common/content_client.h"
 #include "content/public/common/page_transition_types.h"
 #include "content/public/common/referrer.h"
+#include "content/public/common/url_constants.h"
 #include "ipc/ipc_sender.h"
 #include "net/base/net_util.h"
 #include "third_party/WebKit/public/platform/WebCursorInfo.h"
@@ -143,6 +144,11 @@ RendererOverridesHandler::RendererOverridesHandler()
       base::Bind(
           &RendererOverridesHandler::PageSetTouchEmulationEnabled,
           base::Unretained(this)));
+  RegisterCommandHandler(
+      devtools::Page::canEmulate::kName,
+      base::Bind(
+          &RendererOverridesHandler::PageCanEmulate,
+          base::Unretained(this)));
   RegisterCommandHandler(
       devtools::Page::canScreencast::kName,
       base::Bind(
@@ -564,6 +570,24 @@ RendererOverridesHandler::PageSetTouchEmulationEnabled(
   return NULL;
 }
 
+scoped_refptr<DevToolsProtocol::Response>
+RendererOverridesHandler::PageCanEmulate(
+    scoped_refptr<DevToolsProtocol::Command> command) {
+  base::DictionaryValue* result = new base::DictionaryValue();
+#if defined(OS_ANDROID)
+  result->SetBoolean(devtools::kResult, false);
+#else
+  if (WebContents* web_contents = WebContents::FromRenderViewHost(host_)) {
+    result->SetBoolean(
+        devtools::kResult,
+        !web_contents->GetVisibleURL().SchemeIs(kChromeDevToolsScheme));
+  } else {
+    result->SetBoolean(devtools::kResult, true);
+  }
+#endif  // defined(OS_ANDROID)
+  return command->SuccessResponse(result);
+}
+
 scoped_refptr<DevToolsProtocol::Response>
 RendererOverridesHandler::PageCanScreencast(
     scoped_refptr<DevToolsProtocol::Command> command) {

content/browser/devtools/renderer_overrides_handler.h

@@ -84,6 +84,8 @@ class CONTENT_EXPORT RendererOverridesHandler
       scoped_refptr<DevToolsProtocol::Command> command);
   scoped_refptr<DevToolsProtocol::Response> PageCaptureScreenshot(
       scoped_refptr<DevToolsProtocol::Command> command);
+  scoped_refptr<DevToolsProtocol::Response> PageCanEmulate(
+      scoped_refptr<DevToolsProtocol::Command> command);
   scoped_refptr<DevToolsProtocol::Response> PageCanScreencast(
       scoped_refptr<DevToolsProtocol::Command> command);
   scoped_refptr<DevToolsProtocol::Response> PageStartScreencast(