Load the blit framebuffer extension entry points.

src/libANGLE/renderer/gl/FunctionsGL.cpp

@@ -853,6 +853,8 @@ void FunctionsGL::initialize()
         AssignGLEntryPoint(loadProcAddress("glTexSubImage2D"), &texSubImage2D);
 
         // Extensions
+        AssignGLExtensionEntryPoint(extensions, "GL_EXT_framebuffer_blit", loadProcAddress("glBlitFramebufferEXT"), &blitFramebuffer);
+
         AssignGLExtensionEntryPoint(extensions, "GL_KHR_debug", loadProcAddress("glDebugMessageControl"), &debugMessageControl);
         AssignGLExtensionEntryPoint(extensions, "GL_KHR_debug", loadProcAddress("glDebugMessageInsert"), &debugMessageInsert);
         AssignGLExtensionEntryPoint(extensions, "GL_KHR_debug", loadProcAddress("glDebugMessageCallback"), &debugMessageCallback);

src/libANGLE/renderer/gl/renderergl_utils.cpp

@@ -155,6 +155,7 @@ void GenerateCaps(const FunctionsGL *functions, gl::Caps *caps, gl::TextureCapsM
     extensions->textureNPOT = true;
     extensions->textureStorage = true;
     extensions->fboRenderMipmap = true;
+    extensions->framebufferBlit = (functions->blitFramebuffer != nullptr);
     extensions->framebufferMultisample = caps->maxSamples > 0;
     extensions->fence = std::find(functions->extensions.begin(), functions->extensions.end(), "GL_NV_fence") != functions->extensions.end();
 }