[110] Disable SwiftShader for WebGL on M1 Macs.

SwiftShader's LLVM 10 doesn't fully support code generation on ARM.
Continue to support SwiftShader for rasterization which is used in
testing and explicitly requested through flags.

(cherry picked from commit ceef12f)

Bug: chromium:1378476
Change-Id: If452edabb9ca385cb40dbb33c9591814bd862396
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4133390
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1088867}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4143761
Reviewed-by: Prudhvikumar Bommana <pbommana@google.com>
Commit-Queue: Prudhvikumar Bommana <pbommana@google.com>
Cr-Commit-Position: refs/branch-heads/5481@{#159}
Cr-Branched-From: 130f3e4-refs/heads/main@{#1084008}

ui/gl/gl_context_egl.cc

@@ -20,6 +20,10 @@
 #include "ui/gl/gl_gl_api_implementation.h"
 #include "ui/gl/gl_surface_egl.h"
 
+#if BUILDFLAG(IS_APPLE)
+#include "base/mac/mac_util.h"
+#endif
+
 #ifndef EGL_CHROMIUM_create_context_bind_generates_resource
 #define EGL_CHROMIUM_create_context_bind_generates_resource 1
 #define EGL_CONTEXT_BIND_GENERATES_RESOURCE_CHROMIUM 0x33AD
@@ -174,6 +178,18 @@ bool GLContextEGL::Initialize(GLSurface* compatible_surface,
 
   bool is_swangle = IsSoftwareGLImplementation(GetGLImplementationParts());
 
+#if BUILDFLAG(IS_APPLE)
+  if (is_swangle && attribs.webgl_compatibility_context &&
+      base::mac::GetCPUType() == base::mac::CPUType::kArm) {
+    // crbug.com/1378476: LLVM 10 is used as the JIT compiler for SwiftShader,
+    // which doesn't fully support ARM. Disable Swiftshader on ARM CPUs for
+    // WebGL until LLVM is upgraded.
+    DVLOG(1) << __FUNCTION__
+             << ": Software WebGL contexts are not supported on ARM MacOS.";
+    return false;
+  }
+#endif
+
   if (gl_display_->ext->b_EGL_EXT_create_context_robustness || is_swangle) {
     DVLOG(1) << "EGL_EXT_create_context_robustness supported.";
     context_attributes.push_back(EGL_CONTEXT_OPENGL_ROBUST_ACCESS_EXT);