--- a/dom/canvas/WebGL2ContextDraw.cpp
+++ b/dom/canvas/WebGL2ContextDraw.cpp
@@ -8,12 +8,12 @@
 namespace mozilla {
 
 // -------------------------------------------------------------------------
 // Writing to the drawing buffer
 
 void
 WebGL2Context::DrawRangeElements(GLenum mode, GLuint start, GLuint end, GLsizei count, GLenum type, GLintptr offset)
 {
-    MOZ_CRASH("Not Implemented.");
+    GenerateWarning("drawRangeElements: Not Implemented.");
 }
 
 } // namespace mozilla

--- a/dom/canvas/WebGL2ContextFramebuffers.cpp
+++ b/dom/canvas/WebGL2ContextFramebuffers.cpp
@@ -328,23 +328,23 @@ WebGL2Context::BlitFramebuffer(GLint src
     gl->fBlitFramebuffer(srcX0, srcY0, srcX1, srcY1,
                          dstX0, dstY0, dstX1, dstY1,
                          mask, filter);
 }
 
 void
 WebGL2Context::FramebufferTextureLayer(GLenum target, GLenum attachment, GLuint texture, GLint level, GLint layer)
 {
-    MOZ_CRASH("Not Implemented.");
+    GenerateWarning("framebufferTextureLayer: Not Implemented.");
 }
 
 void
 WebGL2Context::GetInternalformatParameter(JSContext*, GLenum target, GLenum internalformat, GLenum pname, JS::MutableHandleValue retval)
 {
-    MOZ_CRASH("Not Implemented.");
+    GenerateWarning("getInternalformatParameter: Not Implemented.");
 }
 
 // Map attachments intended for the default buffer, to attachments for a non-
 // default buffer.
 static bool
 TranslateDefaultAttachments(const dom::Sequence<GLenum>& in, dom::Sequence<GLenum>* out)
 {
     for (size_t i = 0; i < in.Length(); i++) {

--- a/dom/canvas/WebGL2ContextTextures.cpp
+++ b/dom/canvas/WebGL2ContextTextures.cpp
@@ -426,41 +426,41 @@ WebGL2Context::TexSubImage3D(GLenum rawT
 }
 
 void
 WebGL2Context::TexSubImage3D(GLenum target, GLint level,
                              GLint xoffset, GLint yoffset, GLint zoffset,
                              GLenum format, GLenum type, dom::ImageData* data,
                              ErrorResult& rv)
 {
-    MOZ_CRASH("Not Implemented.");
+    GenerateWarning("texSubImage3D: Not implemented.");
 }
 
 void
 WebGL2Context::CopyTexSubImage3D(GLenum target, GLint level,
                                  GLint xoffset, GLint yoffset, GLint zoffset,
                                  GLint x, GLint y, GLsizei width, GLsizei height)
 {
-    MOZ_CRASH("Not Implemented.");
+    GenerateWarning("copyTexSubImage3D: Not implemented.");
 }
 
 void
 WebGL2Context::CompressedTexImage3D(GLenum target, GLint level, GLenum internalformat,
                                     GLsizei width, GLsizei height, GLsizei depth,
                                     GLint border, GLsizei imageSize, const dom::ArrayBufferView& data)
 {
-    MOZ_CRASH("Not Implemented.");
+    GenerateWarning("compressedTexImage3D: Not implemented.");
 }
 
 void
 WebGL2Context::CompressedTexSubImage3D(GLenum target, GLint level, GLint xoffset, GLint yoffset, GLint zoffset,
                                        GLsizei width, GLsizei height, GLsizei depth,
                                        GLenum format, GLsizei imageSize, const dom::ArrayBufferView& data)
 {
-    MOZ_CRASH("Not Implemented.");
+    GenerateWarning("compressedTexSubImage3D: Not implemented.");
 }
 
 JS::Value
 WebGL2Context::GetTexParameterInternal(const TexTarget& target, GLenum pname)
 {
     switch (pname) {
         case LOCAL_GL_TEXTURE_BASE_LEVEL:
         case LOCAL_GL_TEXTURE_COMPARE_FUNC: