Fix std::string use-after-frees in GPUShaderModule::Create

Bug: None
Change-Id: I6a9f7a2bda46e786a3137a6a8e9a84948a301678
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2337102
Commit-Queue: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Austin Eng <enga@chromium.org>
Auto-Submit: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Cr-Commit-Position: refs/heads/master@{#794767}

third_party/blink/renderer/modules/webgpu/gpu_shader_module.cc

@@ -21,13 +21,14 @@ GPUShaderModule* GPUShaderModule::Create(
   WGPUShaderModuleDescriptor dawn_desc = {};
   WGPUShaderModuleWGSLDescriptor wgsl_desc = {};
   WGPUShaderModuleSPIRVDescriptor spirv_desc = {};
+  std::string wgsl_code;
 
   auto wgsl_or_spirv = webgpu_desc->code();
   if (wgsl_or_spirv.IsUSVString()) {
-    std::string code = wgsl_or_spirv.GetAsUSVString().Utf8();
+    wgsl_code = wgsl_or_spirv.GetAsUSVString().Utf8();
 
     wgsl_desc.chain.sType = WGPUSType_ShaderModuleWGSLDescriptor;
-    wgsl_desc.source = code.c_str();
+    wgsl_desc.source = wgsl_code.c_str();
     dawn_desc.nextInChain = reinterpret_cast<WGPUChainedStruct*>(&wgsl_desc);
   } else {
     DCHECK(wgsl_or_spirv.IsUint32Array());
@@ -48,8 +49,10 @@ GPUShaderModule* GPUShaderModule::Create(
     dawn_desc.nextInChain = reinterpret_cast<WGPUChainedStruct*>(&spirv_desc);
   }
 
+  std::string label;
   if (webgpu_desc->hasLabel()) {
-    dawn_desc.label = webgpu_desc->label().Utf8().data();
+    label = webgpu_desc->label().Utf8();
+    dawn_desc.label = label.c_str();
   }
 
   return MakeGarbageCollected<GPUShaderModule>(