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

content/shell/shell.cc

Index: content/shell/shell.cc
diff --git a/content/shell/shell.cc b/content/shell/shell.cc
index fcf684ce5e5d825b054f0f8a805e6decb3c1fb10..0162c5af2c87ff22b642224e5f4175e2b88564f6 100644
--- a/content/shell/shell.cc
+++ b/content/shell/shell.cc
@@ -4,11 +4,16 @@
 
 #include "content/shell/shell.h"
 
+#include "base/command_line.h"
 #include "base/message_loop.h"
 #include "base/path_service.h"
 #include "base/string_util.h"
+#include "content/browser/renderer_host/render_view_host.h"
 #include "content/browser/tab_contents/navigation_controller_impl.h"
 #include "content/browser/tab_contents/tab_contents.h"
+#include "content/public/browser/web_contents_observer.h"
+#include "content/shell/shell_messages.h"
+#include "content/shell/shell_switches.h"
 #include "ui/gfx/size.h"
 
 // Content area size for newly created windows.
@@ -17,6 +22,48 @@ static const int kTestWindowHeight = 600;
 
 namespace content {
 
+namespace {
+
+class ShellObserver : public WebContentsObserver {
+ public:
+  explicit ShellObserver(WebContents* web_contents);
+  virtual ~ShellObserver();
+
+ private:
+  // WebContentsObserver overrides.
+  virtual void DidFinishLoad(int64 frame_id,
+                             const GURL& validated_url,
+                             bool is_main_frame) OVERRIDE;
+  virtual void WebContentsDestroyed(WebContents* web_contents) OVERRIDE;
+
+  DISALLOW_COPY_AND_ASSIGN(ShellObserver);
+};
+
+ShellObserver::ShellObserver(WebContents* web_contents)
+    : WebContentsObserver(web_contents) {
+}
+
+ShellObserver::~ShellObserver() {
+}
+
+void ShellObserver::DidFinishLoad(int64 frame_id,

[jam, 2012/01/27 18:22:30]

nit: up to you, but if a class is declared and defined in a cc file, it's always
shorter (and IMO more readable) to inline all the methods). 

+                                  const GURL& validated_url,
+                                  bool is_main_frame) {
+  if (!is_main_frame)
+    return;
+  if (!CommandLine::ForCurrentProcess()->HasSwitch(switches::kDumpRenderTree))
+    return;
+  RenderViewHost* render_view_host = web_contents()->GetRenderViewHost();
+  render_view_host->Send(
+      new ShellViewMsg_CaptureTextDump(render_view_host->routing_id(), false));
+}
+
+void ShellObserver::WebContentsDestroyed(WebContents* web_contents) {
+  delete this;
+}
+
+}  // namespace
+
 std::vector<Shell*> Shell::windows_;
 
 Shell::Shell()
@@ -64,6 +111,7 @@ Shell* Shell::CreateNewWindow(content::BrowserContext* browser_context,
       routing_id,
       base_tab_contents,
       NULL);
+  new ShellObserver(tab_contents);

[jam, 2012/01/27 18:22:30]

actually, do you need a new WebContentsObserver or can you just make Shell be a
WCO?

   Shell* shell = CreateShell(tab_contents);
   if (!url.is_empty())
     shell->LoadURL(url);