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 402be6321938afe410d03ebdca75f935146caa1a..653ed63b978bfba5ddd42a237c2ed071dfe3d08d 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -1136,6 +1136,10 @@ 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 kEnableSilentDebugging[]       = "enable-silent-debugging";
+
 // 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";