Add blink_platform_unittests.isolate file to bot json files.

testing/buildbot/chromium.android.json

 {
   "Android GN Builder (dbg)": {
     "additional_compile_targets": [
       "blimp_tests",
       "chrome_public_apk",
       "chrome_public_test_apk",
       "content_shell_apk",
       "content_shell_test_apk",
       "system_webview_apk"
     ]
@@ skipping 1120 matching lines @@
       {
         "test": "blimp_unittests"
       },
       {
         "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"
       },
       {
         "args": [
           "--isolate_file_path=src/breakpad/breakpad_unittests.isolate"
         ],
         "override_compile_targets": [
           "breakpad_unittests_deps"
         ],
         "test": "breakpad_unittests"
@@ skipping 249 matching lines @@
       },
       {
         "test": "chrome_sync_shell_test_apk"
       },
       {
         "test": "content_shell_test_apk"
       }
     ]
   }
 }