Add option --dump-render-tree to content_shell to dump the render tree as text.

content/shell/shell_browser_main.cc

Index: content/shell/shell_browser_main.cc
diff --git a/content/shell/shell_browser_main.cc b/content/shell/shell_browser_main.cc
index 311b6a0d813df1cab64e86fbd7d4611809fd8484..8357915c6a1001bcb8f5c8f0b8895e4b65efee81 100644
--- a/content/shell/shell_browser_main.cc
+++ b/content/shell/shell_browser_main.cc
@@ -13,9 +13,11 @@
 #include "content/browser/download/download_file_manager.h"
 #include "content/browser/download/save_file_manager.h"
 #include "content/browser/plugin_service_impl.h"
+#include "content/public/common/main_function_params.h"
 #include "content/shell/shell.h"
 #include "content/shell/shell_browser_context.h"
 #include "content/shell/shell_content_browser_client.h"
+#include "content/shell/shell_switches.h"
 #include "net/base/net_module.h"
 #include "ui/base/clipboard/clipboard.h"
 
@@ -32,7 +34,8 @@ static GURL GetStartupURL() {
 
 ShellBrowserMainParts::ShellBrowserMainParts(
     const content::MainFunctionParams& parameters)
-    : BrowserMainParts() {
+    : BrowserMainParts(),
+      dump_as_text_(parameters.command_line.HasSwitch(switches::kTree)) {
   ShellContentBrowserClient* shell_browser_client =
       static_cast<ShellContentBrowserClient*>(
           content::GetContentClient()->browser());
@@ -48,11 +51,12 @@ void ShellBrowserMainParts::PreMainMessageLoopRun() {
   Shell::PlatformInitialize();
   net::NetModule::SetResourceProvider(Shell::PlatformResourceProvider);
 
-  Shell::CreateNewWindow(browser_context_.get(),
-                         GetStartupURL(),
-                         NULL,
-                         MSG_ROUTING_NONE,
-                         NULL);
+  Shell* shell = Shell::CreateNewWindow(browser_context_.get(),
+                                        GetStartupURL(),
+                                        NULL,
+                                        MSG_ROUTING_NONE,
+                                        NULL);
+  shell->SetDumpAsText(dump_as_text_);
 }
 
 void ShellBrowserMainParts::PostMainMessageLoopRun() {