[DevTools] Handle frontend zoom similarly to tab zoom.

chrome/browser/devtools/devtools_window.cc

Index: chrome/browser/devtools/devtools_window.cc
diff --git a/chrome/browser/devtools/devtools_window.cc b/chrome/browser/devtools/devtools_window.cc
index 5a492a37f5bdb4e5c4531e8f6f5baf8ccb6af0ca..23cd2fd7d412966d6cf9802597ba55ac1f0fa92b 100644
--- a/chrome/browser/devtools/devtools_window.cc
+++ b/chrome/browser/devtools/devtools_window.cc
@@ -19,6 +19,7 @@
 #include "base/values.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/chrome_notification_types.h"
+#include "chrome/browser/chrome_page_zoom.h"
 #include "chrome/browser/extensions/api/debugger/debugger_api.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/extension_web_contents_observer.h"
@@ -852,6 +853,12 @@ void DevToolsWindow::CloseContents(content::WebContents* source) {
   delete web_contents_;
 }
 
+void DevToolsWindow::ContentsZoomChange(bool zoom_in) {
+  DCHECK(is_docked_);
+  chrome_page_zoom::Zoom(web_contents(),
+      zoom_in ? content::PAGE_ZOOM_IN : content::PAGE_ZOOM_OUT);
+}
+
 void DevToolsWindow::BeforeUnloadFired(content::WebContents* tab,
                                        bool proceed,
                                        bool* proceed_to_fire_unload) {