Push API: Avoid false positive DCHECK.

chrome/browser/push_messaging/push_messaging_app_identifier.cc

 // Copyright 2014 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/push_messaging/push_messaging_app_identifier.h"
 
 #include <string.h>
 
 #include "base/guid.h"
 #include "base/logging.h"
@@ skipping 57 matching lines @@
 
   PushMessagingAppIdentifier app_identifier(app_id, origin,
                                             service_worker_registration_id);
   app_identifier.DCheckValid();
   return app_identifier;
 }
 
 // static
 PushMessagingAppIdentifier PushMessagingAppIdentifier::FindByAppId(
     Profile* profile, const std::string& app_id) {
-  // Check case of app_id hasn't been mangled (crbug.com/461867).
+  if (!StartsWithASCII(app_id, kPushMessagingAppIdentifierPrefix,
+                       false /* case_sensitive */)) {
+    return PushMessagingAppIdentifier();
+  }
+
+  // Since we now know this is a Push Messaging app_id, check the case hasn't
+  // been mangled (crbug.com/461867).
+  DCHECK_EQ(kPushMessagingAppIdentifierPrefix, app_id.substr(0, kPrefixLength));
   DCHECK_GE(app_id.size(), kPrefixLength + kGuidLength);
-  DCHECK_EQ(kPushMessagingAppIdentifierPrefix, app_id.substr(0, kPrefixLength));
   DCHECK_EQ(app_id.substr(app_id.size() - kGuidLength),
             StringToUpperASCII(app_id.substr(app_id.size() - kGuidLength)));
 
   const base::DictionaryValue* map =
       profile->GetPrefs()->GetDictionary(prefs::kPushMessagingAppIdentifierMap);
 
   std::string map_value;
   if (!map->GetStringWithoutPathExpansion(app_id, &map_value))
     return PushMessagingAppIdentifier();
 
@@ skipping 102 matching lines @@
     const size_t suffix_length = 1 /* kSeparator */ + kGuidLength;
     DCHECK(app_id_.size() > kPrefixLength + suffix_length);
     DCHECK_EQ(origin_, GURL(app_id_.substr(
         kPrefixLength, app_id_.size() - kPrefixLength - suffix_length)));
     DCHECK_EQ(std::string(1, kSeparator),
               app_id_.substr(app_id_.size() - suffix_length, 1));
   }
   // GUID
   DCHECK(base::IsValidGUID(app_id_.substr(app_id_.size() - kGuidLength)));
 }