Add blink_platform_unittests.isolate file to bot json files.

testing/buildbot/chromium.fyi.json

 {
   "Android Cloud Tests": {
     "gtest_tests": [
       {
         "test": "android_webview_unittests"
       },
       {
         "test": "base_unittests"
       },
       {
@@ skipping 83 matching lines @@
   },
   "Android Tests (trial)(dbg)": {
     "gtest_tests": [
       {
         "args": [
           "--isolate_file_path=src/third_party/WebKit/Source/platform/heap/BlinkHeapUnitTests.isolate"
         ],
         "test": "blink_heap_unittests"
       },
       {
+        "args": [
+          "--isolate_file_path=src/third_party/WebKit/Source/platform/blink_platform_unittests.isolate"
+        ],
         "test": "blink_platform_unittests"
       }
     ],
     "scripts": [
       {
         "name": "telemetry_unittests",
         "script": "telemetry_unittests.py"
       }
     ]
   },
@@ skipping 7580 matching lines @@
       },
       {
         "args": [
           "--isolate-extensions"
         ],
         "test": "unit_tests"
       }
     ]
   }
 }