Clean up image fallback content configuration

Put the setup of the broken image and placeholder elements in a helper
class to make it easier to decipher what is being done, and also what
depends on the ComputedStyle object and not.

Bug: 953707
Change-Id: I675539611e5160e4e31523a1dbcea830fe5c7f18
Commit-Queue: Stephen Chenney <>
Auto-Submit: Fredrik Söderquist <>
Reviewed-by: Stephen Chenney <>
Cr-Commit-Position: refs/heads/master@{#658662}
1 file changed