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There are two main fixes:
-use the new NavigationHandle callbacks on WebContentsObserver which are compatible with PlzNavigate
-update the renderer side so that handles the new order of IPCs: while ReadyToCommitNavigation means the browser side can send its IPC before the internal content ones, with PlzNavigate one content IPC will fire both DidStartProvisionalLoad & DidCommitProvisionalLoad. So add extra logic to the renderer side to handle this.

This fixes
SubresourceFilterBrowserTest.MainFrameActivation
SubresourceFilterBrowserTest.MainFrameActivationOnStartup
SubresourceFilterBrowserTest.SubFrameActivation
with PlzNavigate.

BUG=504347, 653807

Review-Url: https://codereview.chromium.org/2446503002
Cr-Commit-Position: refs/heads/master@{#427085}