Move deg<->rad conversions from cc to ui/gfx/geometry and use them more.

This also aims to eliminate _USE_MATH_DEFINES entirely by removing the last
vestiges of M_PI (at least, from the directories that can depend on ui/gfx).

Bug: none
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Iae16aa804aeb80a750af34b457d426b92dd6c302
Reviewed-on: https://chromium-review.googlesource.com/657905
Reviewed-by: Tim Volodine <timvolodine@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Reviewed-by: Rohit Rao (ping after 24h) <rohitrao@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Ian Vollick <vollick@chromium.org>
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#503069}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: f9f3cebe6abf575ef8bda227a7dee4faa6cd312b

precompile.h

@@ -11,8 +11,6 @@
 
 #define BUILD_PRECOMPILE_H_
 
-#define _USE_MATH_DEFINES
-
 #include <errno.h>
 #include <fcntl.h>
 #include <limits.h>