Adding src side buildbot json for triggering perf jobs on linux perf.

tools/perf/generate_perf_json.py

 #!/usr/bin/env python
 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Script to generate chromium.perf.json and chromium.perf.fyi.json in
 the src/testing/buildbot directory. Maintaining these files by hand is
 too unwieldy.
 """
 
@@ skipping 346 matching lines @@
        'gpu': '8086:1626',
        'os': 'Mac-10.11',
        'device_ids': [
            'build123-b1', 'build124-b1',
            'build125-b1', 'build126-b1', 'build127-b1'
           ]
       }
     ])
 
   waterfall = add_tester(
-    waterfall, 'Linux Perf', 'linux-release', 'linux', num_host_shards=5)
+    waterfall, 'Linux Perf', 'linux-release', 'linux',
+    swarming=[
+      {
+       'gpu': '102b:0534',
+       'os': 'linux',
+       'device_ids': [
+           'build148-m1', 'build149-m1',
+           'build150-m1', 'build151-m1', 'build152-m1'
+          ],
+       'perf_tests': [
+         ('cc_perftests', 2),
+         ('load_library_perf_tests', 2),
+         ('tracing_perftests', 2)]
+      }
+    ])
 
   return waterfall
 
 
 def generate_isolate_script_entry(swarming_dimensions, test_args,
   isolate_name, step_name, override_compile_targets=None):
   result = {
     'args': test_args,
     'isolate_name': isolate_name,
     'name': step_name,
@@ skipping 284 matching lines @@
   waterfall['name'] = 'chromium.perf'
   fyi_waterfall = get_fyi_waterfall_config()
   fyi_waterfall['name'] = 'chromium.perf.fyi'
 
   generate_all_tests(fyi_waterfall)
   generate_all_tests(waterfall)
   return 0
 
 if __name__ == '__main__':
   sys.exit(main())