Add flaky retries for Win7/AMD ANGLE tests.

This test suite seems to be randomly flaky. The retry mechanism
should let the tests pass even if they have up to 2 failures. Even
though they should be 99% deflaked with one retry, give them two
attempts to be 100% sure of not getting a flaky failure. De-flakying
is more important than any other concern.

Also leaves the 'linux_args' setting in the new test spec in case
we end up using it on Linux as well.

Bug: angleproject:5273
Change-Id: Id3deb84b1c5533f37f3b55b9d9659ddc66358544
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2517042Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Cr-Commit-Position: refs/heads/master@{#823646}

testing/buildbot/chromium.gpu.fyi.json

@@ -34527,7 +34527,8 @@
         "args": [
           "angle_end2end_tests",
           "--gtest_filter=-*Vulkan_SwiftShader*",
-          "--bot-mode"
+          "--bot-mode",
+          "--flaky-retries=2"
         ],
         "merge": {
           "args": [],

testing/buildbot/test_suites.pyl

@@ -2000,6 +2000,25 @@
       },
     },
 
+    'gpu_angle_end2end_with_retry_gtests': {
+      'angle_end2end_tests': {
+        'args': [
+          'angle_end2end_tests',
+          '--gtest_filter=-*Vulkan_SwiftShader*',
+          '--bot-mode',
+          '--flaky-retries=2',
+        ],
+        # Linux has issues with creating too many windows at once.
+        'linux_args': [
+          '--max-processes=4',
+        ],
+        'swarming': {
+          'shards': 2,
+        },
+        'use_isolated_scripts_api': True,
+      },
+    },
+
     'gpu_angle_fuchsia_unittests_isolated_scripts': {
       'angle_unittests': {
         'args': [
@@ -5569,7 +5588,7 @@
     ],
 
     'gpu_win_angle_amd_gtests': [
-      'gpu_angle_end2end_gtests',
+      'gpu_angle_end2end_with_retry_gtests',
       'gpu_angle_unit_gtests',
       'gpu_angle_white_box_gtests',
     ],