WebGL Aquarium doesn't render with ANGLE Metal

Blits should not be using the context's write mask,
this leads to missed color information on blits.

Bug: chromium:1257769
Change-Id: Iaf4ff00a727b1bec2424b4d3939fddd4c802a8ea
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3212644
Reviewed-by: Alexey Knyazev <lexa.knyazev@gmail.com>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Kyle Piddington <kpiddington@apple.com>

src/libANGLE/renderer/metal/FrameBufferMtl.mm

@@ -472,10 +472,9 @@ angle::Result FramebufferMtl::blitWithDraw(const gl::Context *context,
         colorBlitParams.srcLevel = srcColorRt->getLevelIndex();
         colorBlitParams.srcLayer = srcColorRt->getLayerIndex();
 
-        colorBlitParams.blitWriteMaskArray = contextMtl->getWriteMaskArray();
-        colorBlitParams.enabledBuffers     = getState().getEnabledDrawBuffers();
-        colorBlitParams.filter             = filter;
-        colorBlitParams.dstLuminance       = srcColorRt->getFormat()->actualAngleFormat().isLUMA();
+        colorBlitParams.enabledBuffers = getState().getEnabledDrawBuffers();
+        colorBlitParams.filter         = filter;
+        colorBlitParams.dstLuminance   = srcColorRt->getFormat()->actualAngleFormat().isLUMA();
 
         ANGLE_TRY(contextMtl->getDisplay()->getUtils().blitColorWithDraw(
             context, renderEncoder, srcColorRt->getFormat()->actualAngleFormat(), colorBlitParams));

src/libANGLE/renderer/metal/mtl_render_utils.h

@@ -80,9 +80,8 @@ struct BlitParams
 
 struct ColorBlitParams : public BlitParams
 {
-    ColorBlitParams() { blitWriteMaskArray.fill(MTLColorWriteMaskAll); }
+    ColorBlitParams() {}
 
-    WriteMaskArray blitWriteMaskArray;
     gl::DrawBufferMask enabledBuffers;
     GLenum filter               = GL_NEAREST;
     bool unpackPremultiplyAlpha = false;

src/libANGLE/renderer/metal/mtl_render_utils.mm

@@ -1487,8 +1487,7 @@ id<MTLRenderPipelineState> ColorBlitUtils::getColorBlitRenderPipelineState(
     RenderPipelineDesc pipelineDesc;
     const RenderPassDesc &renderPassDesc = cmdEncoder->renderPassDesc();
 
-    renderPassDesc.populateRenderPipelineOutputDesc(params.blitWriteMaskArray,
-                                                    &pipelineDesc.outputDescriptor);
+    renderPassDesc.populateRenderPipelineOutputDesc(&pipelineDesc.outputDescriptor);
 
     // Disable blit for some outputs that are not enabled
     pipelineDesc.outputDescriptor.updateEnabledDrawBuffers(params.enabledBuffers);