Bug 1793526 - Remove IsCurrent checks in webgl code. r=gfx-reviewers,lsalzman

Webgl uses mImplicitMakeCurrent these days, so don't worry about it
directly.

Differential Revision: https://phabricator.services.mozilla.com/D188524

dom/canvas/WebGLContextGL.cpp

@@ -1061,7 +1061,6 @@ static bool ValidateReadPixelsFormatAndType(
 
   ////
 
-  MOZ_ASSERT(gl->IsCurrent());
   const auto implPI = webgl->ValidImplementationColorReadPI(srcUsage);
   if (pi == implPI) return true;
 

dom/canvas/WebGLRenderbuffer.cpp

@@ -24,8 +24,6 @@ static GLenum DepthFormatForDepthStencilEmu(gl::GLContext* gl) {
 }
 
 static GLuint DoCreateRenderbuffer(gl::GLContext* gl) {
-  MOZ_ASSERT(gl->IsCurrent());
-
   GLuint ret = 0;
   gl->fGenRenderbuffers(1, &ret);
   return ret;