Allow chrome.debugger API to attach to extension background pages.

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index 755ff6728bea49decececdae67c64c732524541a..f5f1f0661d238fff018db3c8db7894d401e79b83 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -1128,6 +1128,10 @@ const char kRecordMode[]                    = "record-mode";
 // Uses custom front-end URL for the remote debugging.
 const char kRemoteDebuggingFrontend[]       = "remote-debugging-frontend";
 
+// Does not show an infobar when an extension attaches to a page using
+// chrome.debugger page. Required to attach to extension background pages.
+const char kExtensionDebuggingSilent[]       = "extension-debugging-silent";
+
 // Enables print preview in the renderer. This flag is generated internally by
 // Chrome and does nothing when directly passed to the browser.
 const char kRendererPrintPreview[]          = "renderer-print-preview";