chrome: Support Chrome and DevTools command execution (fixes #3282, fixes #3600)

Add new CefBrowserHost::[Can]ExecuteChromeCommand methods for executing
arbitrary Chrome commands.

Add support for existing CefBrowserHost::ShowDevTools, CloseDevTools and
HasDevTools methods.

DevTools windows now support the same Views callbacks as normal popup
windows with the new CefLifeSpanHandler::OnBeforeDevToolsPopup callback
as the DevTools-specific equivalent of OnBeforePopup.

Always create DevTools as an undocked window to support use of
ShowDevTools with default Chrome browser windows.

To test:

Run `ceftests --enable-chrome-runtime [--use-views]
     --gtest_filter=V8Test.OnUncaughtExceptionDevTools`

OR:

1. Run `cefclient --enable-chrome-runtime [--use-native]`
2. Select "Show DevTools", "Close DevTools" or "Inspect" from the
   right-click menu.
3. Notice that the DevTools window is Views-hosted (or native-hosted)
   and works as expected.

Add --use-default-popup to get a default styled popup in step 3.

libcef/browser/chrome/chrome_browser_delegate.h

@@ -39,6 +39,9 @@ class ChromeBrowserHostImpl;
 // but the Browser object will change when the tab is dragged between windows.
 class ChromeBrowserDelegate : public cef::BrowserDelegate {
  public:
+  // The |create_params| and |opener| values are specified via the
+  // Browser::CreateParams passed to Browser::Create. |opener| will only be
+  // specified for certain special Browser types.
   ChromeBrowserDelegate(Browser* browser,
                         const CefBrowserCreateParams& create_params,
                         const Browser* opener);
@@ -49,6 +52,10 @@ class ChromeBrowserDelegate : public cef::BrowserDelegate {
   ~ChromeBrowserDelegate() override;
 
   // cef::BrowserDelegate methods:
+  Browser* CreateDevToolsBrowser(
+      Profile* profile,
+      Browser* opener,
+      std::unique_ptr<content::WebContents>& devtools_contents) override;
   std::unique_ptr<content::WebContents> AddWebContents(
       std::unique_ptr<content::WebContents> new_contents) override;
   void OnWebContentsCreated(content::WebContents* new_contents) override;
@@ -104,18 +111,31 @@ class ChromeBrowserDelegate : public cef::BrowserDelegate {
       content::WebContents* source,
       const content::NativeWebKeyboardEvent& event) override;
 
+  void SetPendingShowDevToolsParams(
+      std::unique_ptr<CefShowDevToolsParams> params);
+
   Browser* browser() const { return browser_; }
 
  private:
-  void CreateBrowser(
+  CefRefPtr<ChromeBrowserHostImpl> CreateBrowserHost(
       content::WebContents* web_contents,
-      CefBrowserSettings settings,
+      const CefBrowserSettings& settings,
       CefRefPtr<CefClient> client,
       std::unique_ptr<CefBrowserPlatformDelegate> platform_delegate,
       scoped_refptr<CefBrowserInfo> browser_info,
+      bool is_devtools_popup,
       CefRefPtr<ChromeBrowserHostImpl> opener,
       CefRefPtr<CefRequestContextImpl> request_context_impl);
 
+  CefRefPtr<ChromeBrowserHostImpl> CreateBrowserHostForPopup(
+      content::WebContents* web_contents,
+      const CefBrowserSettings& settings,
+      CefRefPtr<CefClient> client,
+      CefRefPtr<CefDictionaryValue> extra_info,
+      std::unique_ptr<CefBrowserPlatformDelegate> platform_delegate,
+      bool is_devtools_popup,
+      CefRefPtr<ChromeBrowserHostImpl> opener);
+
   CefBrowserContentsDelegate* GetDelegateForWebContents(
       content::WebContents* web_contents);
 
@@ -130,6 +150,8 @@ class ChromeBrowserDelegate : public cef::BrowserDelegate {
   absl::optional<bool> show_status_bubble_;
   absl::optional<SkRegion> draggable_region_;
   mutable absl::optional<bool> frameless_pip_;
+
+  std::unique_ptr<CefShowDevToolsParams> pending_show_devtools_params_;
 };
 
 #endif  // CEF_LIBCEF_BROWSER_CHROME_CHROME_BROWSER_DELEGATE_H_