Move DocumentSubresourceFilter to core/common.

This removes the DocumentSubresourceFilter's dependency on Blink, and will
allow DSF to be used both from the renderer and the browser side without
violating DEPS rules.

This CL also adds WebDocumentSubresourceFilterImpl, a render-side wrapper
around DSF that implements blink's WebDocumentSubresourceFilter interface.
Basically, this class is equivalent to the DocumentSubresourceFilter class
prior to this CL.

BUG=637415
TBR=dcheng@chromium.org

Review-Url: https://codereview.chromium.org/2697363005
Cr-Commit-Position: refs/heads/master@{#451375}
17 files changed