Remove old wtf/ directory.

The removal comes with various fixups in several places:

(1) Various BUILD.gn files are updated so they point to the new location;
(2) Code generator templates in Source/build are fixed; and
(3) Other random references to old wtf/ are fixed.

BUG=691465
R=haraken@chromium.org,thakis@chromium.org,yzshen@chromium.org,dcheng@chromium.org

Review-Url: https://codereview.chromium.org/2822953002
Cr-Original-Commit-Position: refs/heads/master@{#464941}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: c36ab84ca29ae39938ab91463ca9b3fc0569ee31
154 files changed
tree: 4b825dc642cb6eb9a060e54bf8d69288fbee4904

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