Rename GetAllowedUsage to GetUsage.

Resources used to have both a current and an allowed usage but the
concept of current usage has been removed so we can rename "allowed
usage" to "usage" to make the name match WebGPU's
WebGPUBufferDescriptor::usage and WebGPUTextureDescriptor::usage

Change-Id: I5190950bf7f7f5b86c92247ef0240fead9886268

src/dawn_native/Buffer.cpp

diff --git a/src/dawn_native/Buffer.cpp b/src/dawn_native/Buffer.cpp
index 7211176..7666592 100644
--- a/src/dawn_native/Buffer.cpp
+++ b/src/dawn_native/Buffer.cpp
@@ -25,7 +25,7 @@
     // Buffer
 
     BufferBase::BufferBase(BufferBuilder* builder)
-        : mDevice(builder->mDevice), mSize(builder->mSize), mAllowedUsage(builder->mAllowedUsage) {
+        : mDevice(builder->mDevice), mSize(builder->mSize), mUsage(builder->mAllowedUsage) {
     }
 
     BufferBase::~BufferBase() {
@@ -47,8 +47,8 @@
         return mSize;
     }
 
-    dawn::BufferUsageBit BufferBase::GetAllowedUsage() const {
-        return mAllowedUsage;
+    dawn::BufferUsageBit BufferBase::GetUsage() const {
+        return mUsage;
     }
 
     void BufferBase::CallMapReadCallback(uint32_t serial,
@@ -147,7 +147,7 @@
             DAWN_RETURN_ERROR("Buffer subdata out of range");
         }
 
-        if (!(mAllowedUsage & dawn::BufferUsageBit::TransferDst)) {
+        if (!(mUsage & dawn::BufferUsageBit::TransferDst)) {
             DAWN_RETURN_ERROR("Buffer needs the transfer dst usage bit");
         }
 
@@ -166,7 +166,7 @@
             DAWN_RETURN_ERROR("Buffer already mapped");
         }
 
-        if (!(mAllowedUsage & requiredUsage)) {
+        if (!(mUsage & requiredUsage)) {
             DAWN_RETURN_ERROR("Buffer needs the correct map usage bit");
         }