Fixed possible file handle leak
Automatically flush the cache when an edit is completed.

This will remove the need for applications to manually flush
the cache.
Synchronize isClosed.

See https://github.com/square/okhttp/issues/151

Conflicts:
	src/main/java/com/jakewharton/disklrucache/DiskLruCache.java
Java 5 does have these and IntelliJ keeps complaining.
Add `abortUnlessCommitted` method for use in `finally` blocks.
Add getLength method to Snapshot
Switch to OkHttp as URL's preferred HTTP implementation.

Change-Id: Id724b75dd78b68ed00f5db4989c4070896996ec0

Conflicts:
	JavaLibrary.mk
	luni/src/main/java/libcore/net/http/HttpEngine.java
	luni/src/main/java/libcore/net/http/HttpURLConnectionImpl.java

Conflicts:
	JavaLibrary.mk
	luni/src/main/java/libcore/net/http/HttpEngine.java
	luni/src/main/java/libcore/net/http/HttpURLConnectionImpl.java
Fix URLConnectionTest after latest okhttp update.

I've observed 14 failing tests both before and after
the update.

Change-Id: I40dfd9efe35ed03d89b38b030d3c7b6558b247e2