dawn_native: Fixup namespace from backend:: to dawn_native::

src/dawn_native/opengl/PipelineLayoutGL.cpp

diff --git a/src/dawn_native/opengl/PipelineLayoutGL.cpp b/src/dawn_native/opengl/PipelineLayoutGL.cpp
index 9bc0c5a..4f5c5a4 100644
--- a/src/dawn_native/opengl/PipelineLayoutGL.cpp
+++ b/src/dawn_native/opengl/PipelineLayoutGL.cpp
@@ -18,7 +18,7 @@
 #include "dawn_native/BindGroupLayout.h"
 #include "dawn_native/opengl/DeviceGL.h"
 
-namespace backend { namespace opengl {
+namespace dawn_native { namespace opengl {
 
     PipelineLayout::PipelineLayout(Device* device, const dawn::PipelineLayoutDescriptor* descriptor)
         : PipelineLayoutBase(device, descriptor) {
@@ -77,4 +77,4 @@
         return mNumSampledTextures;
     }
 
-}}  // namespace backend::opengl
+}}  // namespace dawn_native::opengl