[dawn][emscripten] Add if undefined guard for maxImmediateSize.

- Failing in google3 roll without an explicit guard for the new
  limit value.

No-Try: true
Change-Id: I3c94732c6c2ed26ed04ca0382db47ba440991f70
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/242374
Commit-Queue: Kai Ninomiya <kainino@chromium.org>
Auto-Submit: Loko Kung <lokokung@google.com>
Commit-Queue: Loko Kung <lokokung@google.com>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>

third_party/emdawnwebgpu/pkg/webgpu/src/library_webgpu.js

diff --git a/third_party/emdawnwebgpu/pkg/webgpu/src/library_webgpu.js b/third_party/emdawnwebgpu/pkg/webgpu/src/library_webgpu.js
index 625121d..27086ea 100644
--- a/third_party/emdawnwebgpu/pkg/webgpu/src/library_webgpu.js
+++ b/third_party/emdawnwebgpu/pkg/webgpu/src/library_webgpu.js
@@ -574,7 +574,9 @@
       setLimitValueU32('maxComputeWorkgroupsPerDimension', {{{ C_STRUCTS.WGPULimits.maxComputeWorkgroupsPerDimension }}});
 
       // Non-standard. If this is undefined, it will correctly just cast to 0.
-      setLimitValueU32('maxImmediateSize', {{{ C_STRUCTS.WGPULimits.maxImmediateSize }}});
+      if (limits.maxImmediateSize !== undefined) {
+        setLimitValueU32('maxImmediateSize', {{{ C_STRUCTS.WGPULimits.maxImmediateSize }}});
+      }
     },
 
     fillAdapterInfoStruct: (info, infoStruct) => {