[Cronet] Separate Cronet implementation and API by package name.

components/cronet/android/api/src/org/chromium/net/UserAgent.java

 // 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.
 
 package org.chromium.net;
 
 import android.content.Context;
 import android.content.pm.PackageInfo;
 import android.content.pm.PackageManager;
 import android.content.pm.PackageManager.NameNotFoundException;
@@ skipping 39 matching lines @@
             builder.append("; ");
             builder.append(model);
         }
 
         String id = Build.ID;
         if (id.length() > 0) {
             builder.append("; Build/");
             builder.append(id);
         }
 
-        builder.append("; Cronet/");
-        builder.append(Version.CRONET_VERSION);
+        builder.append(";");
+        appendCronetVersion(builder);
 
         builder.append(')');
 
         return builder.toString();
     }
 
     /**
      * Constructs default QUIC User Agent Id string including application name
      * and Cronet version.
      * @param context the context to fetch the application name from.
      * @return User-Agent string.
      */
     static String getQuicUserAgentIdFrom(Context context) {
         StringBuilder builder = new StringBuilder();
 
         // Application name and cronet version.
         builder.append(context.getPackageName());
-        builder.append(" Cronet/");
-        builder.append(Version.CRONET_VERSION);
+        appendCronetVersion(builder);
 
         return builder.toString();
     }
 
     private static int versionFromContext(Context context) {
         synchronized (sLock) {
             if (sVersionCode == VERSION_CODE_UNINITIALIZED) {
                 PackageManager packageManager = context.getPackageManager();
                 String packageName = context.getPackageName();
                 try {
                     PackageInfo packageInfo = packageManager.getPackageInfo(
                             packageName, 0);
                     sVersionCode = packageInfo.versionCode;
                 } catch (NameNotFoundException e) {
                     throw new IllegalStateException(
                             "Cannot determine package version");
                 }
             }
             return sVersionCode;
         }
     }
+
+    private static void appendCronetVersion(StringBuilder builder) {
+        builder.append(" Cronet/");
+        // TODO(pauljensen): This is the API version not the implementation
+        // version. The implementation version may be more appropriate for the
+        // UserAgent but is not available until after the CronetEngine is
+        // instantiated. Down the road, if the implementation is loaded via
+        // other means, this should be replaced with the implementation version.
+        builder.append(ApiVersion.CRONET_VERSION);
+    }
 }