Selectively perform JNI registration in render processes on Android.

base/android/java/src/org/chromium/base/CpuFeatures.java

 // Copyright 2012 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.JNINamespace;
+import org.chromium.base.annotations.MainDex;
 
-// The only purpose of this class is to allow sending CPU properties
-// from the browser process to sandboxed renderer processes. This is
-// needed because sandboxed processes cannot, on ARM, query the kernel
-// about the CPU's properties by parsing /proc, so this operation must
-// be performed in the browser process, and the result passed to
-// renderer ones.
-//
-// For more context, see http://crbug.com/164154
-//
-// Technically, this is a wrapper around the native NDK cpufeatures
-// library. The exact CPU features bits are never used in Java so
-// there is no point in duplicating their definitions here.
-//
+/**
+ * The only purpose of this class is to allow sending CPU properties
+ * from the browser process to sandboxed renderer processes. This is
+ * needed because sandboxed processes cannot, on ARM, query the kernel
+ * about the CPU's properties by parsing /proc, so this operation must
+ * be performed in the browser process, and the result passed to
+ * renderer ones.
+ *
+ * For more context, see http://crbug.com/164154
+ *
+ * Technically, this is a wrapper around the native NDK cpufeatures
+ * library. The exact CPU features bits are never used in Java so
+ * there is no point in duplicating their definitions here.
+ */
 @JNINamespace("base::android")
+@MainDex

[Torne, 2017/01/09 16:43:32]

Might be cleaner to land the added @MainDex requirements in a separate CL first,
since presumably it doesn't depend on anything?

[estevenson, 2017/01/12 03:46:49]

Done.

 public abstract class CpuFeatures {
     /**
      * Return the number of CPU Cores on the device.
      */
     public static int getCount() {
         return nativeGetCoreCount();
     }
 
     /**
      * Return the CPU feature mask.
      * This is a 64-bit integer that corresponds to the CPU's features.
      * The value comes directly from android_getCpuFeatures().
      */
     public static long getMask() {
         return nativeGetCpuFeatures();
     }
 
     private static native int nativeGetCoreCount();
     private static native long nativeGetCpuFeatures();
 }