[devtools] Support different encodings for Page.CaptureScreenshot.

testing/buildbot/chromium.mac.json

Index: testing/buildbot/chromium.mac.json
diff --git a/testing/buildbot/chromium.mac.json b/testing/buildbot/chromium.mac.json
index 72133986d4833cad0abad91093f6131695d64d27..710920b230e4227673cf3a8801f85c57d6f53bbd 100644
--- a/testing/buildbot/chromium.mac.json
+++ b/testing/buildbot/chromium.mac.json
@@ -13,6 +13,7 @@
       "pdf_unittests",
       "printing_unittests",
       "skia_unittests",
+      "snapshot_unittests",
       "sql_unittests",
       "storage_unittests",
       "ui_base_unittests",
@@ -302,6 +303,12 @@
         "swarming": {
           "can_use_on_swarming_builders": true
         },
+        "test": "snapshot_unittests"
+      },
+      {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "sql_unittests"
       },
       {
@@ -653,6 +660,12 @@
         "swarming": {
           "can_use_on_swarming_builders": true
         },
+        "test": "snapshot_unittests"
+      },
+      {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "sql_unittests"
       },
       {
@@ -1005,6 +1018,12 @@
         "swarming": {
           "can_use_on_swarming_builders": true
         },
+        "test": "snapshot_unittests"
+      },
+      {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "sql_unittests"
       },
       {
@@ -1345,6 +1364,12 @@
         "swarming": {
           "can_use_on_swarming_builders": true
         },
+        "test": "snapshot_unittests"
+      },
+      {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "sql_unittests"
       },
       {