Fixed failure in "TestTaskQueuePreProcessing00"

[Benglin]

Purpose

This pull request is meant to fix the following test case:

SchedulerIntegrationTests.TestTaskQueuePreProcessing00

The failure was introduced due to a number of different behaviors in both the system and tests:

1. Add task merging for graph updates
2. Run all recorded test case in auto mode

Declarations

Check these iff you believe they are true

• The code base is in a better state after this PR
• The level of testing this PR includes is appropriate

Reviewers

Hi @aparajit-pratap, this is related to the failing test case that you were debugging this morning. Please have a look, thanks!

FYIs

Hi @lukechurch and @ke-yu, just FYI. The new UpdateGraphAsyncTask merging behavior definitely has changed the expected behavior of this test (and one of the two tasks was dropped as expected).

[Benglin]

I need this member to be filled up by the derived class FakeUpdateGraphAsyncTask so that it won't be null when the base method UpdateGraphAsyncTask.CanMergeWithCore is called (this data member will never be null in the usual UpdateGraphAsyncTask).

[aparajit-pratap]

@Benglin to me it looks like @lukechurch has basically merged multiple UpdateGraphAsyncTasks that are essentially executing the same set of nodes into one so in this test case instead of expecting two of them (for the same set of nodes) we can now expect just one of them after the queue is processed. If so, it looks good to me.

[Benglin]

Spot on, @aparajit-pratap! That's exactly why @lukechurch's original PR was created. Merging this in to stabilize the build, thanks again!