Revert "Destroy backend implementation for Buffers"

This reverts commit b6a80b321e.

Reason for revert: dawn_end2end_tests are failing on the Chromium GPU FYI bots. Example here: https://ci.chromium.org/p/chromium/builders/ci/Win10%20FYI%20Release%20%28NVIDIA%29/4226

Original change's description:
> Destroy backend implementation for Buffers
> 
> Destroy can be used to free the GPU memory associated with resources
> without waiting for javascript garbage collection to occur.
> The buffer is validated at submission to the queue.
> So any buffer that has been destroyed before submission, will then
> invalidate the submit and result in an error.
> 
> Bug: dawn:46
> Change-Id: I40df56ce97baef01deea7552d7a6d40b558fc985
> Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/5320
> Reviewed-by: Kai Ninomiya <kainino@chromium.org>
> Commit-Queue: Natasha Lee <natlee@microsoft.com>

TBR=cwallez@chromium.org,kainino@chromium.org,enga@chromium.org,rafael.cintron@microsoft.com,natlee@microsoft.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: dawn:46
Change-Id: Iadf37a8a6675c744207ec7daaa3fd2fde7da3714
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/5480
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Austin Eng <enga@chromium.org>

src/dawn_native/opengl/BufferGL.cpp

@@ -27,10 +27,6 @@ namespace dawn_native { namespace opengl {
         glBufferData(GL_ARRAY_BUFFER, GetSize(), nullptr, GL_STATIC_DRAW);
     }
 
-    Buffer::~Buffer() {
-        DestroyImpl();
-    }
-
     GLuint Buffer::GetHandle() const {
         return mBuffer;
     }
@@ -62,9 +58,4 @@ namespace dawn_native { namespace opengl {
         glUnmapBuffer(GL_ARRAY_BUFFER);
     }
 
-    void Buffer::DestroyImpl() {
-        glDeleteBuffers(1, &mBuffer);
-        mBuffer = 0;
-    }
-
 }}  // namespace dawn_native::opengl

src/dawn_native/opengl/BufferGL.h

@@ -26,7 +26,6 @@ namespace dawn_native { namespace opengl {
     class Buffer : public BufferBase {
       public:
         Buffer(Device* device, const BufferDescriptor* descriptor);
-        ~Buffer();
 
         GLuint GetHandle() const;
 
@@ -35,7 +34,6 @@ namespace dawn_native { namespace opengl {
         void MapReadAsyncImpl(uint32_t serial) override;
         void MapWriteAsyncImpl(uint32_t serial) override;
         void UnmapImpl() override;
-        void DestroyImpl() override;
 
         GLuint mBuffer = 0;
     };