Fix WebRestrictionsClient.java and WebRestrictionsClientResult.java
included while native side is not

The Java side code (WebRestrictionsClient.java and WebRestrictionsClientResult.java)
are included in the Chrome build while the native side (web_restrictions_client.cc
and web_restrictions_client_result.cc) are not.

This change divides web_restrictions_java into two separate targets, and uses
provider_java in Chrome and client_java in webview.

Bug: 683256
Change-Id: Idfcc8f967abd9351e747962d621dafc06607113a
Reviewed-on: https://chromium-review.googlesource.com/527598
Reviewed-by: Richard Coles <torne@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Commit-Queue: Yipeng Wang <yipengw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#478009}

• android_webview/BUILD.gn[diff]
• chrome/android/BUILD.gn[diff]
• components/web_restrictions/BUILD.gn[diff]