Fix UI glitches with a custom analysis test group with a patch

Fix UI glitches with a custom analysis test group with a patch
https://bugs.webkit.org/show_bug.cgi?id=172694

Reviewed by Sam Weinig.

Fix the following UI glitches with perf try bots:
 - Retrying an A/B testing with a patch fails.
 - A patch specified in an test group does not get specified in the configurator.
 - Drag & dropping a patch doesn't work.
 - Results for custom analysis tasks don't get shown.

* public/api/test-groups.php:
(main): Fix a bug that test group's platform does not match that of the request'ed platform. Since each test
group is associated with platform, just use that instead of querying test_configurations. This resulted in
the configurator not being able to find a triggerable in some cases.

* public/v3/components/custom-analysis-task-configurator.js:
(CustomAnalysisTaskConfigurator):
(CustomAnalysisTaskConfigurator.prototype.setCommitSets): Add patches in the commit set.
(CustomAnalysisTaskConfigurator.prototype._setUploadedFilesToUploader): Now clears the exiting uploaded files
Also renamed from _setUploadedFilesIfEmpty.
(CustomAnalysisTaskConfigurator.prototype._setPatchFiles): Added.
(CustomAnalysisTaskConfigurator.prototype.didConstructShadowTree): We no longer update the list of roots
for the comparsion when a new root is added to the baseline.
(CustomAnalysisTaskConfigurator.prototype._configureComparison): Copy over the list of patches and roots when
starting to configure the comparsion.

* public/v3/components/instant-file-uploader.js:
(InstantFileUploader.prototype.clear): Added.
(InstantFileUploader.prototype.didConstructShadowTree): Added event handlers for dragover & drop events to
allow specifying a patch and root using drag & drop. Unfortunately, this still doesn't work in WebKit due to
a bug in our shadow DOM implementation.
(InstantFileUploader.prototype._didFileInputChange):
(InstantFileUploader.prototype._uploadFiles): Extracted from _didFileInputChange.

* public/v3/pages/analysis-task-page.js:
(AnalysisTaskTestGroupPane.prototype.setAnalysisResults): No longer takes metric.
(AnalysisTaskTestGroupPane.cssTemplate): Removed unused rules. Also disallow flexing on the list of test groups
to avoid the name of a test froup from overflowing on top of the results pane.
(AnalysisTaskPage.prototype._assignTestResultsIfPossible): Set setAnalysisResults even when metric is not set
as is the case for a custom analysis task.
(AnalysisTaskPage.prototype._retryCurrentTestGroup): Use createWithCustomConfiguration to allow retrying of
an A/B testing with a patch in a custom analysis task.
(AnalysisTaskPage.prototype._createTestGroupAfterVerifyingCommitSetList):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@217541 268f45cc-cd09-0410-ab3c-d52691b4dbfc