[Android] Migrate javascript settings to a content setting from a pref.

chrome/android/java/src/org/chromium/chrome/browser/preferences/PrefServiceBridge.java

Index: chrome/android/java/src/org/chromium/chrome/browser/preferences/PrefServiceBridge.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/preferences/PrefServiceBridge.java b/chrome/android/java/src/org/chromium/chrome/browser/preferences/PrefServiceBridge.java
index c3005e17b81555db9ea8ccf8dd3c2f87c4c983e8..a27915fd1410469851afe261e8f48ba48cbbe7fb 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/preferences/PrefServiceBridge.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/preferences/PrefServiceBridge.java
@@ -4,7 +4,11 @@
 
 package org.chromium.chrome.browser.preferences;
 
+import android.content.Context;
+import android.content.SharedPreferences;
+import android.preference.PreferenceManager;
 import android.text.TextUtils;
+import android.util.Log;
 
 import org.chromium.base.CalledByNative;
 import org.chromium.base.ThreadUtils;
@@ -31,6 +35,9 @@ public final class PrefServiceBridge {
     public static final int SUPERVISED_USER_FILTERING_WARN = 1;
     public static final int SUPERVISED_USER_FILTERING_BLOCK = 2;
 
+    private static final String MIGRATION_PREF_KEY = "PrefMigrationVersion";
+    private static final int MIGRATION_CURRENT_VERSION = 1;
+
     private static String sProfilePath;
 
     // Object to notify when "clear browsing data" completes.
@@ -143,6 +150,30 @@ public final class PrefServiceBridge {
     }
 
     /**
+     * Migrates (synchronously) the preferences to the most recent version.
+     */
+    public void migratePreferences(Context context) {
+        SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
+        int currentVersion = preferences.getInt(MIGRATION_PREF_KEY, 0);
+        if (currentVersion > MIGRATION_CURRENT_VERSION) {
+            Log.e(LOG_TAG, "Saved preferences version is newer than supported.  Attempting to "
+                    + "run an older version of Chrome without clearing data is unsupported and "
+                    + "the results may be unpredictable.");
+        }
+        while (currentVersion < MIGRATION_CURRENT_VERSION) {
+            switch (currentVersion) {
+                case 0:
+                    nativeMigrateJavascriptPreference();
+                    break;
+                default:
+                    break;
+            }
+            currentVersion++;
+            preferences.edit().putInt(MIGRATION_PREF_KEY, currentVersion).commit();

[newt (away), 2015/02/12 00:48:59]

Why not put this at the end of the loop? Migrating prefs multiple times (in the
case that we crash during migration) should be safe, right? Then you can just
store MIGRATION_CURRENT_VERSION rather than currentVersion.

Also: how about this structure?

if (currentVersion == MIGRATION_CURRENT_VERSION) return;
if (currentVersion <= 0) {
  // migrate to 1
}
if (currentVersion <= 1) {
  // migrate to 2
}
...
preferences.edit().putInt(MIGRATION_PREF_KEY,
MIGRATION_CURRENT_VERSION).commit();

[Ted C, 2015/02/12 01:01:10]

Done...

I was very conflicted on the style, so I'm fine with this.

+        }
+    }
+
+    /**
      * Returns the path to the user's profile directory via a callback. The callback may be
      * called synchronously or asynchronously.
      */
@@ -746,6 +777,7 @@ public final class PrefServiceBridge {
     private native void nativeResetTranslateDefaults();
     private native boolean nativeGetJavaScriptEnabled();
     private native void nativeSetJavaScriptEnabled(boolean enabled);
+    private native void nativeMigrateJavascriptPreference();
     private native void nativeClearBrowsingData(boolean history, boolean cache,
             boolean cookiesAndSiteData, boolean passwords, boolean formData);
     private native void nativeSetAllowCookiesEnabled(boolean allow);