Disable lazy source positions

Flag off by default now since it's causing crashes in the profiler.

R=rmcilroy

Bug: chromium:994673
Change-Id: I92b46e1f90819c0007106d843ecae2c3974eb3c8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1760814
Commit-Queue: Dan Elphick <delphick@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63250}

BUILD.gn

@@ -188,8 +188,8 @@ declare_args() {
   # Sets -DV8_SHARED_RO_HEAP.
   v8_enable_shared_ro_heap = ""
 
-  # Enables lazy source positions by default.
-  v8_enable_lazy_source_positions = true
+  # Disable lazy source positions by default.
+  v8_enable_lazy_source_positions = false
 
   # Disable write barriers when GCs are non-incremental and
   # heap has single generation.