Expose if we are using swiftshader via WebGraphicsContext3DProvider.

third_party/WebKit/Source/platform/graphics/test/FakeWebGraphicsContext3DProvider.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "gpu/command_buffer/client/gles2_interface.h"
 #include "gpu/command_buffer/common/capabilities.h"
 #include "public/platform/WebGraphicsContext3DProvider.h"
 #include "third_party/skia/include/gpu/GrContext.h"
 #include "third_party/skia/include/gpu/gl/GrGLInterface.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 class FakeWebGraphicsContext3DProvider : public WebGraphicsContext3DProvider {
 public:
     FakeWebGraphicsContext3DProvider(gpu::gles2::GLES2Interface* gl)
         : m_gl(gl)
     {
         RefPtr<const GrGLInterface> glInterface = adoptRef(GrGLCreateNullInterface());
         m_grContext = adoptRef(GrContext::Create(kOpenGL_GrBackend, reinterpret_cast<GrBackendContext>(glInterface.get())));
     }
 
     GrContext* grContext() override
     {
         return m_grContext.get();
     }
 
-    gpu::Capabilities getCapabilities()
+    gpu::Capabilities getCapabilities() override
     {
         return gpu::Capabilities();
     }
 
+    bool isSoftwareRendering() const override
+    {
+        return false;
+    }
+
     gpu::gles2::GLES2Interface* contextGL() override
     {
         return m_gl;
     }
 
     bool bindToCurrentThread() override { return false; }
     void setLostContextCallback(WebClosure) override {}
     void setErrorMessageCallback(WebFunction<void(const char*, int32_t id)>) {}
 
 private:
     gpu::gles2::GLES2Interface* m_gl;
     RefPtr<GrContext> m_grContext;
 };
 
 } // namespace blink