9482 Re-enable embedder_unittests. (cla: yes)

9483 Reland “IOS Platform view transform/clipping (#9075)” and fix the breakage. (cla: yes)

9485 Add –observatory-host switch (cla: yes)

9486 Rework image & texture management to use concurrent message queues. (cla: yes)

9489 Handle ambiguous directionality of final trailing whitespace in mixed bidi text (cla: yes)

9490 fix a bug where the platform view’s transform is not reset before set frame (cla: yes)

9491 Purge caches on low memory on iOS (cla: yes)

9493 Run benchmarks on try jobs. (cla: yes)

9495 fix build breakage on PlatformViews.mm (cla: yes)