DevTools: support live coverage
- support polling in CoverageModel and CoverageView
- support incremental updates in CoverageListView
- revise the way decorators are shown, make a dummy decorator and then iterate over all lines in UISourceCode, map them to original file locations and check coverage
- remove remains of mixed coverage decorators
- assume whitespace is always unused
BUG=719113
Review-Url: https://codereview.chromium.org/2865573003
Cr-Commit-Position: refs/heads/master@{#469856}
20 files changed
