chrome: Add ability to handle chrome menu/keyboard commands (fixes issue #3280)

This change adds a CefCommandHandler::OnChromeCommand callback for optionally
handling Chrome commands triggered via menus or keyboard shortcuts. Supported
command IDs are listed in a new cef_command_ids.h header file.

To test: Run `cefclient --enable-chrome-runtime --hide-controls`. Most commands
will blocked and removed from context menus.

libcef/browser/chrome/browser_delegate.h

@@ -10,6 +10,7 @@
 
 #include "base/memory/scoped_refptr.h"
 #include "content/public/browser/web_contents_delegate.h"
+#include "ui/base/window_open_disposition.h"
 
 class Browser;
 
@@ -47,6 +48,13 @@ class BrowserDelegate : public content::WebContentsDelegate {
   virtual bool ShowStatusBubble(bool show_by_default) {
     return show_by_default;
   }
+
+  // Return true to handle (or disable) a command. ID values come from
+  // chrome/app/chrome_command_ids.h.
+  virtual bool HandleCommand(int command_id,
+                             WindowOpenDisposition disposition) {
+    return false;
+  }
 };
 
 }  // namespace cef

libcef/browser/chrome/chrome_browser_delegate.cc

@@ -88,6 +88,20 @@ bool ChromeBrowserDelegate::ShowStatusBubble(bool show_by_default) {
   return *show_status_bubble_;
 }
 
+bool ChromeBrowserDelegate::HandleCommand(int command_id,
+                                          WindowOpenDisposition disposition) {
+  if (auto browser = ChromeBrowserHostImpl::GetBrowserForBrowser(browser_)) {
+    if (auto client = browser->GetClient()) {
+      if (auto handler = client->GetCommandHandler()) {
+        return handler->OnChromeCommand(
+            browser.get(), command_id,
+            static_cast<cef_window_open_disposition_t>(disposition));
+      }
+    }
+  }
+  return false;
+}
+
 void ChromeBrowserDelegate::WebContentsCreated(
     content::WebContents* source_contents,
     int opener_render_process_id,

libcef/browser/chrome/chrome_browser_delegate.h

@@ -52,6 +52,8 @@ class ChromeBrowserDelegate : public cef::BrowserDelegate {
   void SetAsDelegate(content::WebContents* web_contents,
                      bool set_delegate) override;
   bool ShowStatusBubble(bool show_by_default) override;
+  bool HandleCommand(int command_id,
+                     WindowOpenDisposition disposition) override;
 
   // WebContentsDelegate methods:
   void WebContentsCreated(content::WebContents* source_contents,