Repository: flutter
Issue: Engine tests have lots of non-fatal errors and warnings
Labels: team,engine,P3,c: tech-debt,team-engine,triaged-engine

Running the engine tests, I see lots of error and warning messages:
```
...
[ERROR:flutter/shell/platform/embedder/embedder.cc(646)] Required compositor callbacks absent.
embedder.cc (1111): 'FlutterEngineInitialize' returned 'kInvalidArguments'. Compositor arguments were invalid.
...
[ERROR:flutter/flow/layers/platform_view_layer.cc(25)] Trying to embed a platform view but the PrerollContext does not support embedding
[ERROR:flutter/flow/layers/platform_view_layer.cc(40)] Trying to embed a platform view but the PaintContext does not support embedding
...
embedder.cc (703): 'FlutterEngineCreateAOTData' returned 'kInvalidArguments'. Null source specified.
embedder.cc (705): 'FlutterEngineCreateAOTData' returned 'kInvalidArguments'. Null data_out specified.
embedder.cc (747): 'FlutterEngineCreateAOTData' returned 'kInvalidArguments'. Invalid FlutterEngineAOTDataSourceType type specified.
embedder.cc (712): 'FlutterEngineCreateAOTData' returned 'kInvalidArguments'. Invalid ELF path specified.
embedder.cc (712): 'FlutterEngineCreateAOTData' returned 'kInvalidArguments'. Invalid ELF path specified.
embedder.cc (735): 'FlutterEngineCreateAOTData' returned 'kInvalidArguments'. Could not find isolate snapshot data.
...
Dart Error: Invalid loading unit
Dart Error: Invalid loading unit
...
[ERROR:flutter/runtime/dart_isolate.cc(699)] Could not resolve main entrypoint function.
[ERROR:flutter/runtime/dart_isolate.cc(190)] Could not run the run main Dart entrypoint.
[ERROR:flutter/testing/dart_isolate_runner.cc(136)] Could not create running isolate.
Dart Unhandled Exception: NoSuchMethodError: No top-level getter 'thisShouldNotExist' declared.
Receiver: top-level
Tried calling: thisShouldNotExist, stack trace: #0      NoSuchMethodError._throwNew (dart:core-patch/errors_patch.dart:212)
...
[ERROR:flutter/runtime/dart_isolate_unittests.cc(266)] Hello from Dart!
flutter: In function canRegisterNativeCallback
flutter: Called native method from canRegisterNativeCallback
...
GMOCK WARNING:
Uninteresting mock function call - returning default value.
    Function call: GetFrameBudget()
          Returns: 8-byte object <00-00 00-00 00-00 00-00>
NOTE: You can safely ignore the above warning unless this call should not happen.  Do not suppress it by blindly adding an EXPECT_CALL() if you don't mean to enforce the call.  See https://github.com/google/googletest/blob/master/googlemock/docs/cook_book.md#knowing-when-to-expect for details.

GMOCK WARNING:
Uninteresting mock function call - returning default value.
    Function call: GetContext()
          Returns: NULL
NOTE: You can safely ignore the above warning unless this call should not happen.  Do not suppress it by blindly adding an EXPECT_CALL() if you don't mean to enforce the call.  See https://github.com/google/googletest/blob/master/googlemock/docs/cook_book.md#knowing-when-to-expect for details.
```

Having these messages makes it hard to determine what is actually broken when things are broken. (Our style guide, for this reason, says to only log messages that are actionable.)