Look at canonical decl, when deciding whether to rename or not.

This is motivated by an observation that before this CL
blink::V8Document::openMethodCustom got renamed, even though
it has its declaration in a generated header (only the definition
of the method is in a non-generated source file).

BUG=682835

Review-Url: https://codereview.chromium.org/2640283003
Cr-Commit-Position: refs/heads/master@{#445466}
3 files changed