blink::Page: Move main_frame declaration

Page::main_frame_ is used during constructing Page::visual_viewport_
(VisualViewport) which imples that the field should be constructed
before using.

allocatd memory.

Note: In practice this works because Oilpan currently 0-fills all newly
Change-Id: I103d90c17d649dffbce2c9ac70a0a6a9cac9448b
Reviewed-on: https://chromium-review.googlesource.com/1133159
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574139}
2 files changed