Make _incremental usable by instrumentation tests

build/android/incremental_install/java/org/chromium/incrementalinstall/BootstrapApplication.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.incrementalinstall;
 
 import android.app.Application;
 import android.app.Instrumentation;
 import android.content.ComponentName;
 import android.content.Context;
@@ skipping 100 matching lines @@
     }
 
     /**
      * Returns the fully-qualified class name for the given key, stored in a
      * <meta> witin the manifest.
      */
     private String getClassNameFromMetadata(String key) throws NameNotFoundException {
         ApplicationInfo appInfo = getPackageManager().getApplicationInfo(getPackageName(),
                 PackageManager.GET_META_DATA);
         String value = appInfo.metaData.getString(key);
-        if (!value.contains(".")) {
+        if (value != null && !value.contains(".")) {
             value = getPackageName() + "." + value;
         }
         return value;
     }
 
     /**
      * Instantiates and initializes mRealInstrumentation (the real Instrumentation class).
      */
     private void initInstrumentation(String realInstrumentationName)
             throws ReflectiveOperationException {
+        Instrumentation oldInstrumentation =
+                (Instrumentation) Reflect.getField(mActivityThread, "mInstrumentation");
+        if (realInstrumentationName == null) {
+            // This is the case when an incremental app is used as a target for an instrumentation
+            // test. In this case, ActivityThread can instantiate the proper class just fine since
+            // it exists within the test apk (as opposed to the incremental apk-under-test).
+            Log.i(TAG, "Running with external instrumentation");
+            mRealInstrumentation = oldInstrumentation;
+            return;
+        }
+        // For unit tests, the instrumentation class is replaced in the manifest by a build step
+        // because ActivityThread tries to instantiate it before we get a chance to load the
+        // incremental dex files.
         Log.i(TAG, "Instantiating instrumentation " + realInstrumentationName);
         mRealInstrumentation = (Instrumentation) Reflect.newInstance(
                 Class.forName(realInstrumentationName));
-        Instrumentation oldInstrumentation =
-                (Instrumentation) Reflect.getField(mActivityThread, "mInstrumentation");
 
         // Initialize the fields that are set by Instrumentation.init().
         String[] initFields = {"mThread", "mMessageQueue", "mInstrContext", "mAppContext",
                 "mWatcher", "mUiAutomationConnection"};
         for (String fieldName : initFields) {
             Reflect.setField(mRealInstrumentation, fieldName,
                     Reflect.getField(oldInstrumentation, fieldName));
         }
         // But make sure the correct ComponentName is used.
         ComponentName newName = new ComponentName(
@@ skipping 79 matching lines @@
             for (Map.Entry<String, WeakReference<?>> entry : packageMap.entrySet()) {
                 Object loadedApk = entry.getValue().get();
                 if (loadedApk != null && Reflect.getField(loadedApk, "mApplication") == this) {
                     Reflect.setField(loadedApk, "mApplication", mRealApplication);
                     Reflect.setField(mRealApplication, "mLoadedApk", loadedApk);
                 }
             }
         }
     }
 }