[Cronet] Clear mock cert verifier reference in CronetEngine.Builder

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

 // 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.
 
 package org.chromium.net;
 
 import android.content.Context;
 import android.support.annotation.IntDef;
 import android.util.Log;
 
@@ skipping 364 matching lines @@
             } catch (JSONException e) {
                 // Intentionally do nothing.
             }
             return this;
         }
 
         /**
          * Build a {@link CronetEngine} using this builder's configuration.
          */
         public CronetEngine build() {
-            return createContext(this);
+            CronetEngine engine = createContext(this);
+            // Clear MOCK_CERT_VERIFIER reference if there is any, since
+            // the ownership has been transferred to the engine.
+            mConfig.remove(CronetEngineBuilderList.MOCK_CERT_VERIFIER);
+            return engine;
         }
     }
 
     private static final String TAG = "UrlRequestFactory";
     private static final String CRONET_URL_REQUEST_CONTEXT =
             "org.chromium.net.CronetUrlRequestContext";
 
     /**
      * Creates a {@link UrlRequest} object. All callbacks will
      * be called on {@code executor}'s thread. {@code executor} must not run
@@ skipping 290 matching lines @@
                 cronetEngine = possibleEngine;
             }
         } catch (ClassNotFoundException e) {
             // Leave as null.
         } catch (Exception e) {
             throw new IllegalStateException("Cannot instantiate: " + CRONET_URL_REQUEST_CONTEXT, e);
         }
         return cronetEngine;
     }
 }