Rename namespace dawn_native to dawn::native.

But keep a namespace alias to avoid breaking project that depend on the
previous namespace name while they get updated.

Done with through the following steps:

 - git grep -l dawn_native:: | xargs sed -i "" "s/dawn_native::/dawn::native::/g"
 - git grep -l "namespace dawn_native" | xargs sed -i "" "s/namespace dawn_native/namespace dawn::native/g"
 - git cl format
 - Manual fixups in generator/templates (and the addition of
   namespace_case in dawn_json_generator.py).
 - The addition of the namespace alias in DawnNative.h

Bug: dawn:824
Change-Id: I676cc4e3ced2e0e4bab32a0d66d7eaf9537e3f09
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/75982
Reviewed-by: Loko Kung <lokokung@google.com>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Auto-Submit: Corentin Wallez <cwallez@chromium.org>

src/include/dawn_native/D3D12Backend.h

@@ -28,7 +28,7 @@
 struct ID3D12Device;
 struct ID3D12Resource;
 
-namespace dawn_native::d3d12 {
+namespace dawn::native::d3d12 {
 
     class D3D11on12ResourceCache;
 
@@ -106,6 +106,6 @@ namespace dawn_native::d3d12 {
         Microsoft::WRL::ComPtr<IDXGIAdapter> dxgiAdapter;
     };
 
-}  // namespace dawn_native::d3d12
+}  // namespace dawn::native::d3d12
 
 #endif  // DAWNNATIVE_D3D12BACKEND_H_

src/include/dawn_native/DawnNative.h

@@ -31,7 +31,7 @@ namespace wgpu {
     struct DeviceDescriptor;
 }
 
-namespace dawn_native {
+namespace dawn::native {
 
     class InstanceBase;
     class AdapterBase;
@@ -247,6 +247,9 @@ namespace dawn_native {
     DAWN_NATIVE_EXPORT bool BindGroupLayoutBindingsEqualForTesting(WGPUBindGroupLayout a,
                                                                    WGPUBindGroupLayout b);
 
-}  // namespace dawn_native
+}  // namespace dawn::native
+
+// TODO(dawn:824): Remove once the deprecation period is passed.
+namespace dawn_native = dawn::native;
 
 #endif  // DAWNNATIVE_DAWNNATIVE_H_

src/include/dawn_native/MetalBackend.h

@@ -32,7 +32,7 @@ typedef __IOSurface* IOSurfaceRef;
 #    import <Metal/Metal.h>
 #endif  //__OBJC__
 
-namespace dawn_native::metal {
+namespace dawn::native::metal {
 
     struct DAWN_NATIVE_EXPORT AdapterDiscoveryOptions : public AdapterDiscoveryOptionsBase {
         AdapterDiscoveryOptions();
@@ -56,14 +56,14 @@ namespace dawn_native::metal {
     // scheduled could lead to races in who gets scheduled first and incorrect rendering.
     DAWN_NATIVE_EXPORT void WaitForCommandsToBeScheduled(WGPUDevice device);
 
-}  // namespace dawn_native::metal
+}  // namespace dawn::native::metal
 
 #ifdef __OBJC__
-namespace dawn_native::metal {
+namespace dawn::native::metal {
 
     DAWN_NATIVE_EXPORT id<MTLDevice> GetMetalDevice(WGPUDevice device);
 
-}  // namespace dawn_native::metal
+}  // namespace dawn::native::metal
 #endif  // __OBJC__
 
 #pragma clang diagnostic pop

src/include/dawn_native/NullBackend.h

@@ -18,8 +18,8 @@
 #include <dawn/dawn_wsi.h>
 #include <dawn_native/DawnNative.h>
 
-namespace dawn_native::null {
+namespace dawn::native::null {
     DAWN_NATIVE_EXPORT DawnSwapChainImplementation CreateNativeSwapChainImpl();
-}  // namespace dawn_native::null
+}  // namespace dawn::native::null
 
 #endif  // DAWNNATIVE_NULLBACKEND_H_

src/include/dawn_native/OpenGLBackend.h

@@ -20,7 +20,7 @@ typedef void* EGLImage;
 #include <dawn/dawn_wsi.h>
 #include <dawn_native/DawnNative.h>
 
-namespace dawn_native::opengl {
+namespace dawn::native::opengl {
 
     struct DAWN_NATIVE_EXPORT AdapterDiscoveryOptions : public AdapterDiscoveryOptionsBase {
         AdapterDiscoveryOptions();
@@ -50,6 +50,6 @@ namespace dawn_native::opengl {
     DAWN_NATIVE_EXPORT WGPUTexture
     WrapExternalEGLImage(WGPUDevice device, const ExternalImageDescriptorEGLImage* descriptor);
 
-}  // namespace dawn_native::opengl
+}  // namespace dawn::native::opengl
 
 #endif  // DAWNNATIVE_OPENGLBACKEND_H_

src/include/dawn_native/VulkanBackend.h

@@ -22,7 +22,7 @@
 
 #include <vector>
 
-namespace dawn_native::vulkan {
+namespace dawn::native::vulkan {
 
     DAWN_NATIVE_EXPORT VkInstance GetInstance(WGPUDevice device);
 
@@ -135,6 +135,6 @@ namespace dawn_native::vulkan {
                                                   VkImageLayout desiredLayout,
                                                   ExternalImageExportInfoVk* info);
 
-}  // namespace dawn_native::vulkan
+}  // namespace dawn::native::vulkan
 
 #endif  // DAWNNATIVE_VULKANBACKEND_H_