[android_webview] Introduce AwAssets to reference assets inside the apk.
This change introduces a utility class AwAssets, accessible by native,
which is able to retrieve references (fd + offset + size) of assets
inside the apk. This is to enable direct mmap of uncompressed assets.
This change does NOT introduce yet any change to the WebView apk itself.
At current state, no behavioral change is intended.
BUG=394502
Review URL: https://codereview.chromium.org/
401743003
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284238 0039d316-1c4b-4281-b951-d872f2087c98