Keep chrome_sizes on Win10 1703

We are not yet migrating chrome.tests pool. Until we move bots
from 1703 to 1909, keep chrome_sizes on previous version so
they are not starved for resources.

Bug: 1124829
Change-Id: I780bb5e6e4b23ccb30c27efb769afd14eb6f6116
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2488740Reviewed-by: Erik Staab <estaab@chromium.org>
Commit-Queue: Ian Struiksma <ianstruiksma@google.com>
Cr-Commit-Position: refs/heads/master@{#819131}

testing/buildbot/chrome.json

@@ -6721,7 +6721,7 @@
           "can_use_on_swarming_builders": true,
           "dimension_sets": [
             {
-              "os": "Windows-10-18363",
+              "os": "Windows-10-15063",
               "pool": "chrome.tests"
             }
           ],
@@ -6747,7 +6747,7 @@
           "can_use_on_swarming_builders": true,
           "dimension_sets": [
             {
-              "os": "Windows-10-18363",
+              "os": "Windows-10-15063",
               "pool": "chrome.tests"
             }
           ],

testing/buildbot/test_suite_exceptions.pyl

@@ -856,6 +856,32 @@
       }
     }
   },
+  'chrome_sizes': {
+    'modifications': {
+      'win-chrome': {
+        'swarming': {
+          # TODO(crbug.com/1124829): Remove this exception once pool
+          # chrome.tests is migrated to 1909.
+          'dimension_sets': [
+            {
+              'os': 'Windows-10-15063',
+            },
+          ],
+        },
+      },
+      'win64-chrome': {
+        'swarming': {
+          # TODO(crbug.com/1124829): Remove this exception once pool
+          # chrome.tests is migrated to 1909.
+          'dimension_sets': [
+            {
+              'os': 'Windows-10-15063',
+            },
+          ],
+        },
+      },
+    },
+  },
   'chromedriver_py_tests': {
     'remove_from': [
       # Timeout happens sometimes (crbug.com/951799).