dawn_conversions: replace CString with std::unique_ptr<char[]>

CString is being removed. Also, this was sort of relying on
an implementation detail of CString, and this fixes that.

Bug: 950077
Change-Id: I4fab8de0ef8f3202c0144dcea8eeedf89e90ce77
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1648712Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Gyuyoung Kim <gyuyoung@igalia.com>
Commit-Queue: Kai Ninomiya <kainino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#667238}

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

@@ -577,18 +577,24 @@ DawnOrigin3D AsDawnType(const GPUOrigin3D* webgpu_origin) {
   return dawn_origin;
 }
 
-std::tuple<DawnPipelineStageDescriptor, CString> AsDawnType(
+OwnedPipelineStageDescriptor AsDawnType(
     const GPUPipelineStageDescriptor* webgpu_stage) {
   DCHECK(webgpu_stage);
 
-  CString entry_point_string(webgpu_stage->entryPoint().Ascii().c_str());
+  std::string entry_point = webgpu_stage->entryPoint().Ascii();
+  // length() is in bytes (not utf-8 characters or something), so this is ok.
+  size_t byte_size = entry_point.length() + 1;
+
+  std::unique_ptr<char[]> entry_point_keepalive =
+      std::make_unique<char[]>(byte_size);
+  char* entry_point_ptr = entry_point_keepalive.get();
+  memcpy(entry_point_ptr, entry_point.c_str(), byte_size);
+
   DawnPipelineStageDescriptor dawn_stage;
   dawn_stage.module = webgpu_stage->module()->GetHandle();
-  dawn_stage.entryPoint = entry_point_string.data();
+  dawn_stage.entryPoint = entry_point_ptr;
 
-  // CString holds a scoped_refptr to the string data so it is valid to move
-  // it into the return value without invalidating the entryPoint.
-  return std::make_tuple(dawn_stage, std::move(entry_point_string));
+  return std::make_tuple(dawn_stage, std::move(entry_point_keepalive));
 }
 
 }  // namespace blink

third_party/blink/renderer/modules/webgpu/dawn_conversions.h

@@ -40,8 +40,10 @@ DawnEnum AsDawnEnum(const WTF::String& webgpu_enum);
 DawnColor AsDawnType(const GPUColor*);
 DawnExtent3D AsDawnType(const GPUExtent3D*);
 DawnOrigin3D AsDawnType(const GPUOrigin3D*);
-std::tuple<DawnPipelineStageDescriptor, CString> AsDawnType(
-    const GPUPipelineStageDescriptor*);
+
+using OwnedPipelineStageDescriptor =
+    std::tuple<DawnPipelineStageDescriptor, std::unique_ptr<char[]>>;
+OwnedPipelineStageDescriptor AsDawnType(const GPUPipelineStageDescriptor*);
 
 // WebGPU objects are converted to Dawn objects by getting the opaque handle
 // which can be passed to Dawn.

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

@@ -209,13 +209,12 @@ GPURenderPipeline* GPURenderPipeline::Create(
   dawn_desc.nextInChain = nullptr;
   dawn_desc.layout = AsDawnType(webgpu_desc->layout());
 
-  using PipelineStageInfo = std::tuple<DawnPipelineStageDescriptor, CString>;
-
-  PipelineStageInfo vertex_stage_info = AsDawnType(webgpu_desc->vertexStage());
+  OwnedPipelineStageDescriptor vertex_stage_info =
+      AsDawnType(webgpu_desc->vertexStage());
   dawn_desc.vertexStage = &std::get<0>(vertex_stage_info);
 
   // TODO(crbug.com/dawn/136): Support vertex-only pipelines.
-  PipelineStageInfo fragment_stage_info =
+  OwnedPipelineStageDescriptor fragment_stage_info =
       AsDawnType(webgpu_desc->fragmentStage());
   dawn_desc.fragmentStage = &std::get<0>(fragment_stage_info);