DevTools: CPUFlameChart: stick function entry color to the function name and url.

The old color generator had the dependency from line number too and it was a bad idea because
after a change in the source file the entry would change the color.

Also the entry colors had implicit dependency from the order of processing.

BUG=382116
R=alph@chromium.org

Review URL: https://codereview.chromium.org/319363002

git-svn-id: svn://svn.chromium.org/blink/trunk@175787 bbb929c8-8fbe-4397-9dbb-9b2b20218538