Links in platform apps should open in the system default browser.

chrome/browser/ui/extensions/shell_window.cc

Index: chrome/browser/ui/extensions/shell_window.cc
diff --git a/chrome/browser/ui/extensions/shell_window.cc b/chrome/browser/ui/extensions/shell_window.cc
index bcfe4d28c14d6a0ffc9add047aea9043438e5922..ffaf9afb2463eb67e7af7c64ec378a9dc403b44c 100644
--- a/chrome/browser/ui/extensions/shell_window.cc
+++ b/chrome/browser/ui/extensions/shell_window.cc
@@ -13,6 +13,7 @@
 #include "chrome/browser/infobars/infobar_tab_helper.h"
 #include "chrome/browser/intents/web_intents_util.h"
 #include "chrome/browser/lifetime/application_lifetime.h"
+#include "chrome/browser/platform_util.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/sessions/session_id.h"
 #include "chrome/browser/ui/browser.h"
@@ -63,6 +64,40 @@ void SuspendRenderViewHost(RenderViewHost* rvh) {
 
 }  // namespace
 
+// ExternalWebContentImpl is Web content delegate for link navigation.
+// It helps to open URL in system default browser.
+class ExternalWebContentImpl : public content::WebContentsDelegate {
+ public:
+  ExternalWebContentImpl() {}
+  virtual ~ExternalWebContentImpl() {}
+
+ private:
+  // content::WebContentsDelegate implementation.
+  virtual content::WebContents* OpenURLFromTab(
+      content::WebContents* source,
+      const content::OpenURLParams& params) OVERRIDE;
+
+  DISALLOW_COPY_AND_ASSIGN(ExternalWebContentImpl);
+};
+
+content::WebContents* ExternalWebContentImpl::OpenURLFromTab(
+    content::WebContents* source,
+    const content::OpenURLParams& params) {
+#if defined(OS_MACOSX)
+  // This must run on the UI thread on OS X.
+  platform_util::OpenExternal(params.url);
+#else
+  // Otherwise put this work on the file thread. On Windows ShellExecute may
+  // block for a significant amount of time, and it shouldn't hurt on Linux.
+  BrowserThread::PostTask(
+      BrowserThread::FILE,
+      FROM_HERE,
+      base::Bind(&platform_util::OpenExternal, params.url));
+#endif
+
+  return NULL;
+}
+
 ShellWindow::CreateParams::CreateParams()
   : frame(ShellWindow::CreateParams::FRAME_CHROME),
     bounds(-1, -1, kDefaultWidth, kDefaultHeight),
@@ -259,6 +294,12 @@ void ShellWindow::AddNewContents(WebContents* source,
   DCHECK(source == web_contents_);
   DCHECK(Profile::FromBrowserContext(new_contents->GetBrowserContext()) ==
       profile_);
+
+#if defined(OS_WIN) || defined(OS_MACOSX) || defined(OS_POSIX)

[Mihai Parparita -not on Chrome, 2012/09/05 18:15:10]

What platform are you looking to avoid here? Chrome OS? I believe OS_POSIX is
true there. I think OS_LINUX is more appropriate.

+  if (!external_content_delegate_.get())
+    external_content_delegate_.reset(new ExternalWebContentImpl());

[Mihai Parparita -not on Chrome, 2012/09/05 18:15:10]

Seems like ExternalWebContentImpl could be a singleton.

Also, it's not actually a WebContents (or an implementation of one).
ExternalWebContentsDelegate or ExternalUrlWebContentsDelegate or
ExternalUrlController may be better names.

+  new_contents->SetDelegate(external_content_delegate_.get());
+#else
   Browser* browser = browser::FindOrCreateTabbedBrowser(profile_);
   // Force all links to open in a new tab, even if they were trying to open a
   // new window.
@@ -266,6 +307,7 @@ void ShellWindow::AddNewContents(WebContents* source,
       disposition == NEW_BACKGROUND_TAB ? disposition : NEW_FOREGROUND_TAB;
   chrome::AddWebContents(browser, NULL, new_contents, disposition, initial_pos,
                          user_gesture);
+#endif
 }
 
 void ShellWindow::HandleKeyboardEvent(