Add script which gathers JSON output from a Swarming task's shards.

content/test/gpu/generate_buildbot_json.py

Index: content/test/gpu/generate_buildbot_json.py
diff --git a/content/test/gpu/generate_buildbot_json.py b/content/test/gpu/generate_buildbot_json.py
index 79e15273fade9833e1705ad99b5680194366d988..61db377e8d8d5154ca47044b3a63cc41ff1d2fae 100755
--- a/content/test/gpu/generate_buildbot_json.py
+++ b/content/test/gpu/generate_buildbot_json.py
@@ -931,6 +931,11 @@ TELEMETRY_GPU_INTEGRATION_TESTS = {
     'args': [
       '--webgl-conformance-version=2.0.0',
       '--webgl2-only=true',
+      # The current working directory when run via isolate is
+      # out/Debug or out/Release. Reference this file relatively to
+      # it.
+      '--read-abbreviated-json-results-from=' + \
+      '../../content/test/data/gpu/webgl2_conformance_tests_output.json',
     ],
     'swarming': {
       # These tests currently take about an hour to run. Split them
@@ -966,6 +971,11 @@ TELEMETRY_GPU_INTEGRATION_TESTS = {
     'args': [
       '--webgl-conformance-version=2.0.0',
       '--webgl2-only=true',
+      # The current working directory when run via isolate is
+      # out/Debug or out/Release. Reference this file relatively to
+      # it.
+      '--read-abbreviated-json-results-from=' + \
+      '../../content/test/data/gpu/webgl2_conformance_tests_output.json',
     ],
     'swarming': {
       # These tests currently take about an hour to run. Split them