Investigate bug 714841, size regression

Investigate bug 714841, size regression

Apply this patch (based on 2762593002) and note the size regression.

This patch includes crrev.com/2762593002. It also turns on verbose
linking for chrome_child.dll and it converts browser and browser_sources
from source_set to static_library.

Launch bug: https://bugs.chromium.org/p/chromium/issues/detail?id=705916

Add --headless flag to Windows:

Fix browser_tests not compiling properly on windows
Fix headless/BUILD.gn by:
   - Changing headless_lib to a headless component, following steps in https://chromium.googlesource.com/chromium/src/+/master/docs/component_build.md and fixing the build for linux, since it now compiles as a shared_library when component build is true.
   - Adding neccesary HEADLESS_EXPORT (submitted in https://codereview.chromium.org/2775693003/)
   - Disabling breakpad in windows (will fix in a separate CL)

BUG=714841