blink: Reduce the size of execution_context.h

execution_context.h is used in 4,800+ compilation units, and this CL
reduces its estimated expanded size from 3.17MB to 1.95MB.

This CL removes #includes for single_thread_task_runner.h,
security_context.h, and kurl.h from execution_context.h.

Bug: 242216
Change-Id: I2e37b1c58902a58ba3370c26a5a38513ca1e3cbc
Reviewed-on: https://chromium-review.googlesource.com/1102293
Reviewed-by: Hayato Ito <hayato@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568307}
7 files changed