Blank UI for web component tests.

chrome/common/url_constants.cc

Index: chrome/common/url_constants.cc
diff --git a/chrome/common/url_constants.cc b/chrome/common/url_constants.cc
index 0ac097f18b69bb29bd28983b5f09d5ecfe1c7152..f091db9bd40eb55a534be7a88047472ec90a3df2 100644
--- a/chrome/common/url_constants.cc
+++ b/chrome/common/url_constants.cc
@@ -95,6 +95,7 @@ const char kChromeUIUberFrameURL[] = "chrome://uber-frame/";
 const char kChromeUIUserActionsURL[] = "chrome://user-actions/";
 const char kChromeUIVersionURL[] = "chrome://version/";
 const char kChromeUIVoiceSearchURL[] = "chrome://voicesearch/";
+const char kChromeUIWebComponentTestURL[] = "chrome://web-component-test/";
 
 #if defined(OS_ANDROID)
 const char kChromeUINativeScheme[] = "chrome-native";
@@ -260,6 +261,7 @@ const char kChromeUIUberHost[] = "chrome";
 const char kChromeUIUserActionsHost[] = "user-actions";
 const char kChromeUIVersionHost[] = "version";
 const char kChromeUIVoiceSearchHost[] = "voicesearch";
+const char kChromeUIWebComponentTestHost[] = "web-component-test";
 const char kChromeUIWebRTCDeviceProviderHost[] =
     "webrtc-device-provider";
 const char kChromeUIWorkersHost[] = "workers";