Add a specific switch to force enable blimp.

Add a BLIMP_ENABLED switch.
BUG=640736

Review-Url: https://codereview.chromium.org/2299383002
Cr-Commit-Position: refs/heads/master@{#416314}

blimp/client/core/android/java/src/org/chromium/blimp/core/BlimpClientContextImpl.java

@@ -72,7 +72,7 @@ public class BlimpClientContextImpl implements BlimpClientContext, BlimpPreferen
     @Override
     public boolean isBlimpEnabled() {
         return PreferencesUtil.isBlimpEnabled()
-                || CommandLine.getInstance().hasSwitch(BlimpClientSwitches.ENGINE_IP);
+                || CommandLine.getInstance().hasSwitch(BlimpClientSwitches.ENABLE_BLIMP);
     }
 
     @Override

blimp/client/core/android/java/src/org/chromium/blimp/core/BlimpClientSwitches.java

@@ -9,6 +9,8 @@ package org.chromium.blimp.core;
  * portion of Chromium on Android.
  */
 public final class BlimpClientSwitches {
+    // Can be used to force blimp on, bypassing the settings requirements.
+    public static final String ENABLE_BLIMP = "enable-blimp";
 
     // Specifies the engine's IP address. Must be used in conjunction with
     // --engine-port and --engine-transport.