Upstream DocumentTabModelImpl and related classes
Moves the DocumentTabModelImpl and its associated tests/utility classes upstream
from the downstream directories.
Updates the findbugs to remove obsolete ones and add
temporary new ones (until more is upstreamed).
Setting NOTRY to true to get around findbugs changes.
BUG=415747
TEST=DocumentTabModelImplTest, OffTheRecordDocumentTabModelTest
NOTRY=true
Review URL: https://codereview.chromium.org/
802343003
Cr-Commit-Position: refs/heads/master@{#308680}