Assign a color to each line (=category) in the graph of DMP visualizer.
On breaking down a category, DMP visualizer with this CL does not change
colors of categories which are not broken.

Each color code is generated from ID of the category by a hash function.
The function generates same color code for same ID.
It may also generate same color code for different IDs, but it is not
a problem for this objective.


BUG=259206
TEST=Manual

Review URL: https://codereview.chromium.org/27660002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230066 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230066