Reland "Set use_dawn=true on Linux"

This is a reland of 290037a86589a15cfeeaf86e3db466a1f2d04fb7
It's been preceded by a fix to set dawn_use_x11=false to fix
compilation on lacros.

Original change's description:
> Set use_dawn=true on Linux
>
> This enables WebGPU on Linux behind --enable-unsafe-webgpu
> and --enable-features=Vulkan. Shared image support requires
> SkiaRenderer (default on Linux) and Vulkan to be enabled.
>
> Bug: 976495
> Change-Id: I97065f2ac6aadd110971254bfe3526d366318b83
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2368534
> Commit-Queue: Austin Eng <[email protected]>
> Reviewed-by: Kenneth Russell <[email protected]>
> Reviewed-by: Kai Ninomiya <[email protected]>
> Reviewed-by: Corentin Wallez <[email protected]>
> Cr-Commit-Position: refs/heads/master@{#817266}

Bug: 976495
Tbr: [email protected]
Cq-Include-Trybots: luci.chromium.try:linux-lacros-rel
Change-Id: I6bcf6daa48e838bc8e721126f353c97a5eb752e6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2476774
Commit-Queue: Austin Eng <[email protected]>
Reviewed-by: Corentin Wallez <[email protected]>
Cr-Commit-Position: refs/heads/master@{#817664}
diff --git a/gpu/BUILD.gn b/gpu/BUILD.gn
index c90b427..c9bd7768 100644
--- a/gpu/BUILD.gn
+++ b/gpu/BUILD.gn
@@ -359,7 +359,8 @@
     sources += [ "command_buffer/tests/gl_unittests_android.cc" ]
   }
 
-  if (use_dawn) {
+  # Simply loading the Vulkan driver leaks crbug.com/1134681
+  if (use_dawn && !is_lsan) {
     sources += [
       "command_buffer/service/webgpu_decoder_unittest.cc",
       "command_buffer/tests/shared_image_gl_backing_produce_dawn_unittest.cc",