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

chrome/browser/banners/app_banner_debug_log.cc

Index: chrome/browser/banners/app_banner_debug_log.cc
diff --git a/chrome/browser/banners/app_banner_debug_log.cc b/chrome/browser/banners/app_banner_debug_log.cc
new file mode 100644
index 0000000000000000000000000000000000000000..36818b0b6ade365ccece596be18304a58e9c7375
--- /dev/null
+++ b/chrome/browser/banners/app_banner_debug_log.cc
@@ -0,0 +1,59 @@
+// 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.
+
+#include "chrome/browser/banners/app_banner_debug_log.h"
+
+#include "base/command_line.h"
+#include "chrome/common/chrome_switches.h"
+#include "chrome/common/render_messages.h"
+#include "content/public/browser/render_frame_host.h"
+#include "content/public/browser/web_contents.h"
+#include "content/public/browser/web_contents_observer.h"
+
+namespace banners {
+
+const char kRendererRequestCancel[] =
+    "renderer has requested the banner prompt be cancelled";
+const char kManifestEmpty[] = "manifest is empty";
+const char kCannotDetermineBestIcon[] =
+    "could not determine the best icon to use";
+const char kNoMatchingServiceWorker[] =
+    "no matching service worker detected. You may need to reload the page, or "
+    "check that the service worker for the current page also controls the "
+    "start URL from the manifest";
+const char kNoIconAvailable[] = "no icon available to display";
+const char kBannerAlreadyAdded[] =
+    "the banner has already been added to the homescreen";
+const char kUserNavigatedBeforeBannerShown[] =
+    "the user navigated before the banner could be shown";
+const char kStartURLNotValid[] = "start URL in manifest is not valid";
+const char kManifestMissingNameOrShortName[] =
+    "one of manifest name or short name must be specified";
+const char kManifestMissingSuitableIcon[] =
+    "manifest does not contain a suitable icon - PNG format of at least "
+    "144x144px is required";
+const char kNotServedFromSecureOrigin[] =
+    "page not served from a secure origin";
+// The leading space is intentional as another string is prepended.
+const char kIgnoredNotSupportedOnAndroid[] =
+    " application ignored: not supported on Android";
+const char kIgnoredNoId[] = "play application ignored: no id provided";
+
+void OutputDeveloperNotShownMessage(content::WebContents* web_contents,
+                                    const std::string& message) {
+  OutputDeveloperDebugMessage(web_contents, "not shown: " + message);
+}
+
+void OutputDeveloperDebugMessage(content::WebContents* web_contents,
+                                 const std::string& message) {
+  std::string log_message = "App banner " + message;
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kBypassAppBannerEngagementChecks) && web_contents) {
+    web_contents->GetMainFrame()->Send(
+        new ChromeViewMsg_AppBannerDebugMessageRequest(
+            web_contents->GetMainFrame()->GetRoutingID(), log_message));
+  }
+}
+
+}  // namespace banners