Add webusb notification UI code

chrome/browser/chrome_browser_main.cc

Index: chrome/browser/chrome_browser_main.cc
diff --git a/chrome/browser/chrome_browser_main.cc b/chrome/browser/chrome_browser_main.cc
index d9bf84879fd00ab9cd2318518260164b83a1760b..e58af0f607b3713b657b18fa9836689c818dbcf0 100644
--- a/chrome/browser/chrome_browser_main.cc
+++ b/chrome/browser/chrome_browser_main.cc
@@ -237,6 +237,11 @@
 #include "ui/aura/env.h"
 #endif  // defined(USE_AURA)
 
+#if !defined(OS_ANDROID) && !defined(OS_IOS)
+#include "chrome/browser/chrome_webusb_browser_client.h"
+#include "components/webusb/webusb_detector.h"
+#endif
+
 using content::BrowserThread;
 
 namespace {
@@ -1179,6 +1184,15 @@ void ChromeBrowserMainParts::PostBrowserStart() {
       base::TimeDelta::FromMinutes(1));
 #endif  // defined(ENABLE_WEBRTC)
 
+#if !defined(OS_ANDROID) && !defined(OS_IOS)
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableWebUsbNotifications)) {
+    webusb_browser_client_.reset(new ChromeWebUsbBrowserClient());
+    webusb_detector_.reset(
+        new webusb::WebUsbDetector(webusb_browser_client_.get()));
+  }
+#endif
+
   // At this point, StartupBrowserCreator::Start has run creating initial
   // browser windows and tabs, but no progress has been made in loading
   // content as the main message loop hasn't started processing tasks yet.
@@ -1775,6 +1789,11 @@ void ChromeBrowserMainParts::PostMainMessageLoopRun() {
   // shut down.
   process_power_collector_.reset();
 
+#if !defined(OS_IOS)
+  webusb_browser_client_.reset();
+  webusb_detector_.reset();

[stevenjb, 2015/09/09 19:35:26]

Note: We should really reset the detector before the browser client since the
detector depends on the browser client. As-is if the detector code changes to
access the browser client in the destructor, a crash would likely be introduced.

[juncai, 2015/09/09 20:30:29]

Done in a new patch.

+#endif
+
   for (size_t i = 0; i < chrome_extra_parts_.size(); ++i)
     chrome_extra_parts_[i]->PostMainMessageLoopRun();