[WebGPU] Set initial frontFace value to "ccw"

Instead of having web developers to specify a rasterizationState frontFace
value for every singleGPURenderPipelineDescriptor, a default value is now
provided according to spec change.
See https://github.com/gpuweb/gpuweb/pull/313

Bug: 877147
Change-Id: I05b059b9e189c996d8a087b45f4a3e82cffc7df0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1675764
Auto-Submit: François Beaufort <beaufort.francois@gmail.com>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672010}

third_party/blink/renderer/modules/webgpu/gpu_rasterization_state_descriptor.idl

@@ -5,7 +5,7 @@
 // https://github.com/gpuweb/gpuweb/blob/master/design/sketch.webidl
 
 dictionary GPURasterizationStateDescriptor {
-    required GPUFrontFace frontFace;
+    GPUFrontFace frontFace = "ccw";
     GPUCullMode cullMode = "none";
 
     long depthBias = 0;