Correctly track texture cleared state for sharing

Correctly track texture cleared state for sharing

When sharing textures in mailboxes using MailboxManagerSync
there's an optimization that if textures are not updated then
there is no need to share it again. However the code that
checks whether textures are updated ignores the cleared
state, causing shared texture to remain uncleared
indefinitely.

Fix by check the cleared state. And add a unit test.

BUG=453199
Review URL: https://codereview.chromium.org/890453002

Cr-Commit-Position: refs/heads/master@{#313814}
(cherry picked from commit 2f4ff4807f5d7805a5658ceb7ba71072152ea6c9)

TBR=boliu@chromium.org

Committed: https://chromium.googlesource.com/chromium/src/+/ace97840db2a9fa237cdc6038070dfd3aa0bf160

[boliu, 2015-02-04 21:59:36]

Committed patchset #1 (id:1) manually as
ace97840db2a9fa237cdc6038070dfd3aa0bf160 (tree was closed).