[core] In WebGL, if query timer extension is unavailable, return error object for kernelMs profile.

[annxingyuan]

This PR fixes #2624

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This change is 

[annxingyuan]

@nsthorat @dsmilkov ping :D

[nsthorat]

Reviewed 4 of 4 files at r1.
Reviewable status: complete! 1 of 1 approvals obtained (waiting on @annxingyuan, @dsmilkov, and @nsthorat)

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tfjs-core/src/backends/webgl/backend_webgl.ts, line 530 at r1 (raw file):

    };

    if (env().getNumber('WEBGL_DISJOINT_QUERY_TIMER_EXTENSION_VERSION') > 0) {

I think you want WEBGL_DISJOINT_QUERY_TIMER_EXTENSION_RELIABLE

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tfjs-core/src/backends/webgl/backend_webgl.ts, line 538 at r1 (raw file):

              .map(d => `${d.name}: ${d.ms}`)
              .join(', ');
    } else {

possible to add a test for this where we set the flag explicitly to false and check the output?

[dsmilkov]

Reviewed 4 of 4 files at r1.
Reviewable status: complete! 2 of 1 approvals obtained (waiting on @annxingyuan and @dsmilkov)

[dsmilkov]

No additional comments (+1 to Nikhil's comments)

Reviewable status: complete! 2 of 1 approvals obtained (waiting on @annxingyuan and @dsmilkov)

[annxingyuan]

Reviewable status: complete! 2 of 1 approvals obtained

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tfjs-core/src/backends/webgl/backend_webgl.ts, line 530 at r1 (raw file):

Previously, nsthorat (Nikhil Thorat) wrote…

I think you want WEBGL_DISJOINT_QUERY_TIMER_EXTENSION_RELIABLE

Done

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tfjs-core/src/backends/webgl/backend_webgl.ts, line 538 at r1 (raw file):

Previously, nsthorat (Nikhil Thorat) wrote…

possible to add a test for this where we set the flag explicitly to false and check the output?

Done