Selectively perform JNI registration in render processes on Android.

base/android/java/src/org/chromium/base/JNIUtils.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.base;
 
 import org.chromium.base.annotations.CalledByNative;
 import org.chromium.base.annotations.MainDex;
 
 /**
  * This class provides JNI-related methods to the native library.
  */
 @MainDex
 public class JNIUtils {
+    private static boolean sSelectiveJniRegistrationEnabled;
+
     /**
      * This returns a ClassLoader that is capable of loading Chromium Java code. Such a ClassLoader
      * is needed for the few cases where the JNI mechanism is unable to automatically determine the
      * appropriate ClassLoader instance.
      */
     @CalledByNative
     public static Object getClassLoader() {
         return JNIUtils.class.getClassLoader();
     }
+
+    /**
+     * @return whether or not the current process supports selective JNI registration.
+     */
+    @CalledByNative
+    public static boolean isSelectiveJniRegistrationEnabled() {
+        return sSelectiveJniRegistrationEnabled;
+    }
+
+    /**
+     * Allow this process to selectively perform JNI registration. This must be called before
+     * loading native libraries or it will have no effect.
+     */
+    public static void enableSelectiveJniRegistration() {
+        sSelectiveJniRegistrationEnabled = true;

[Ted C, 2017/01/31 17:56:53]

should we make sSelectiveJniRegistrationEnabled a capital B Boolean?  Set it to
null as default, then do like:

public static boolean isSelectiveJniRegistrationEnabled() {
    if (sSelectiveJniRegistrationEnabled == null)
sSelectiveJniRegistrationEnabled = false;
    return sSelectiveJniRegistrationEnabled;
}

public static void enableSelectiveJniRegistration() {
    assert sSelectiveJniRegistrationEnabled == null;
    sSelectiveJniRegistrationEnabled = true;
}

Then we'll be able to catch regressions if we don't set this correctly.

[estevenson, 2017/01/31 18:56:41]

Good call. Done.

+    }
 }