Add an extension bubble explaining which extensions are in dev mode.

chrome/browser/extensions/extension_prefs.cc

Index: chrome/browser/extensions/extension_prefs.cc
diff --git a/chrome/browser/extensions/extension_prefs.cc b/chrome/browser/extensions/extension_prefs.cc
index 21158a511493b133bc5736470c41ce47d74e28ae..402a8066a23d2c6f2e2bda93f5cb22eb23a6dee6 100644
--- a/chrome/browser/extensions/extension_prefs.cc
+++ b/chrome/browser/extensions/extension_prefs.cc
@@ -90,6 +90,7 @@ const char kPrefAcknowledgePromptCount[] = "ack_prompt_count";
 const char kPrefExternalAcknowledged[] = "ack_external";
 const char kPrefBlacklistAcknowledged[] = "ack_blacklist";
 const char kPrefWipeoutAcknowledged[] = "ack_wiped";
+const char kPrefDevModeAcknowledged[] = "ack_devmode";
 
 // Indicates whether the external extension was installed during the first
 // run of this profile.
@@ -691,7 +692,19 @@ void ExtensionPrefs::SetWipeoutAcknowledged(
     const std::string& extension_id,
     bool value) {
   UpdateExtensionPref(extension_id, kPrefWipeoutAcknowledged,
-                      Value::CreateBooleanValue(value));
+                      value ? Value::CreateBooleanValue(value) : NULL);
+}
+
+bool ExtensionPrefs::HasDevModeBeenAcknowledged(
+    const std::string& extension_id) {
+  return ReadPrefAsBooleanAndReturn(extension_id, kPrefDevModeAcknowledged);
+}
+
+void ExtensionPrefs::SetDevModeAcknowledged(
+    const std::string& extension_id,
+    bool value) {
+  UpdateExtensionPref(extension_id, kPrefDevModeAcknowledged,
+                      value ? Value::CreateBooleanValue(value) : NULL);
 }
 
 bool ExtensionPrefs::SetAlertSystemFirstRun() {