Log messages regarding why app banners aren't displayed to the console

chrome/browser/banners/app_banner_debug_log.h

Index: chrome/browser/banners/app_banner_debug_log.h
diff --git a/chrome/browser/banners/app_banner_debug_log.h b/chrome/browser/banners/app_banner_debug_log.h
new file mode 100644
index 0000000000000000000000000000000000000000..dab2733bd2081284e4754b5a8b131cdecdcbf6c4
--- /dev/null
+++ b/chrome/browser/banners/app_banner_debug_log.h
@@ -0,0 +1,43 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_BANNERS_APP_BANNER_DEBUG_LOG_H_
+#define CHROME_BROWSER_BANNERS_APP_BANNER_DEBUG_LOG_H_
+
+#include <string>
+
+namespace content {
+class WebContents;
+}  // namespace content
+
+namespace banners {
+
+// Error message strings used to notify developers via the console.
+extern const char kRendererRequestCancel[];
+extern const char kManifestEmpty[];
+extern const char kCannotDetermineBestIcon[];
+extern const char kNoMatchingServiceWorker[];
+extern const char kNoIconAvailable[];
+extern const char kBannerAlreadyAdded[];
+extern const char kUserNavigatedBeforeBannerShown[];
+extern const char kStartURLNotValid[];
+extern const char kManifestMissingNameOrShortName[];
+extern const char kManifestMissingSuitableIcon[];
+extern const char kNotServedFromSecureOrigin[];
+extern const char kIgnoredNotSupportedOnAndroid[];
+extern const char kIgnoredNoId[];
+
+// Logs a message to the main console if a banner could not be shown
+// and the engagement checks have been bypassed.
+void OutputDeveloperNotShownMessage(content::WebContents* web_contents,
+                                    const std::string& message);
+
+// Logs a debugging message to the main console if the engagement checks have
+// been bypassed.
+void OutputDeveloperDebugMessage(content::WebContents* web_contents,
+                                 const std::string& message);
+
+}  // namespace banners
+
+#endif  // CHROME_BROWSER_BANNERS_APP_BANNER_DEBUG_LOG_H_