Make dawn idl support dynamic buffer offset

This patch simply added dynamic buffer offset in dawn idl and
modify the shape of SetBindGroup.

BUG=dawn:55

Change-Id: I516e08f3ee558ba375a87d98eaea6d60e93d4514
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/5600
Commit-Queue: Shaobo Yan <shaobo.yan@intel.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
diff --git a/dawn.json b/dawn.json
index 5e65d3b..493eeac 100644
--- a/dawn.json
+++ b/dawn.json
@@ -73,7 +73,9 @@
             {"value": 0, "name": "uniform buffer"},
             {"value": 1, "name": "sampler"},
             {"value": 2, "name": "sampled texture"},
-            {"value": 3, "name": "storage buffer"}
+            {"value": 3, "name": "storage buffer"},
+            {"value": 4, "name": "dynamic uniform buffer"},
+            {"value": 5, "name": "dynamic storage buffer"}
         ]
     },
     "blend descriptor": {
@@ -375,7 +377,9 @@
                 "name": "set bind group",
                 "args": [
                     {"name": "group index", "type": "uint32_t"},
-                    {"name": "group", "type": "bind group"}
+                    {"name": "group", "type": "bind group"},
+                    {"name": "dynamic offset count", "type": "uint32_t"},
+                    {"name": "dynamic offsets", "type": "uint32_t", "annotation": "const*", "length": "dynamic offset count"}
                 ]
             },
             {
@@ -776,7 +780,9 @@
                 "name": "set bind group",
                 "args": [
                     {"name": "group index", "type": "uint32_t"},
-                    {"name": "group", "type": "bind group"}
+                    {"name": "group", "type": "bind group"},
+                    {"name": "dynamic offset count", "type": "uint32_t"},
+                    {"name": "dynamic offsets", "type": "uint32_t", "annotation": "const*", "length": "dynamic offset count"}
                 ]
             },
             {