[App Shell] Add dev tools for debugging

apps/shell/browser/shell_browser_main_parts.cc

Index: apps/shell/browser/shell_browser_main_parts.cc
diff --git a/apps/shell/browser/shell_browser_main_parts.cc b/apps/shell/browser/shell_browser_main_parts.cc
index 9afadd09a0bdc0418ff079e5e8c2982faf4ec28f..da87208399c575512c4a8028dad608d797022831 100644
--- a/apps/shell/browser/shell_browser_main_parts.cc
+++ b/apps/shell/browser/shell_browser_main_parts.cc
@@ -15,6 +15,7 @@
 #include "base/run_loop.h"
 #include "components/browser_context_keyed_service/browser_context_dependency_manager.h"
 #include "content/public/common/result_codes.h"
+#include "content/shell/browser/shell_devtools_delegate.h"
 #include "extensions/browser/extension_system.h"
 #include "extensions/browser/renderer_startup_helper.h"
 #include "ui/aura/env.h"
@@ -113,6 +114,9 @@ void ShellBrowserMainParts::PreMainMessageLoopRun() {
   BrowserContextDependencyManager::GetInstance()->CreateBrowserContextServices(
       browser_context_.get());
 
+  devtools_delegate_.reset(
+      new content::ShellDevToolsDelegate(browser_context_.get()));
+
   CreateRootWindow();
   CreateViewsDelegate();
 
@@ -138,6 +142,8 @@ bool ShellBrowserMainParts::MainMessageLoopRun(int* result_code)  {
 }
 
 void ShellBrowserMainParts::PostMainMessageLoopRun() {
+  if (devtools_delegate_)

[James Cook, 2014/02/10 20:31:23]

Why do you need the if()?  It looks like it should always exist.

[Haojian Wu, 2014/02/11 03:24:36]

Yes, in this code logic, it's always valid (it gets reset in
PreMainMessageLoopRun).
But I think it will be better to do this check although it's valid here  since
the pointer initialized NULL when constructing ShellBrowserMainParts object.

[James Cook, 2014/02/11 17:11:16]

I wouldn't do the if() because it confuses the reader -- it makes the reader
think there is a code path where the pointer will be NULL. For example, in
DestroyRootWindow() we don't check if wm_test_helper_ is NULL, even though it
starts as NULL in the constructor. Likewise in CreateExtensionSystem() we don't
check if browser_context_ is NULL.

+    devtools_delegate_->Stop();
   DestroyViewsDelegate();
   DestroyRootWindow();
   BrowserContextDependencyManager::GetInstance()->DestroyBrowserContextServices(