Enable lazy source positions by default

Also adds a compile time flag which allows the default to be configured
so node can disable it since it hangs the node cpu profiler tests.

Bug: v8:8510
Change-Id: Idf4785036dc6242769410091518a67ac9179b718
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1491491Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62089}

BUILD.gn

@@ -187,6 +187,9 @@ declare_args() {
   # Enable sharing read-only space across isolates.
   # Sets -DV8_SHARED_RO_HEAP.
   v8_enable_shared_ro_heap = ""
+
+  # Enables lazy source positions by default.
+  v8_enable_lazy_source_positions = true
 }
 
 # We reuse the snapshot toolchain for building torque and other generators to
@@ -429,6 +432,9 @@ config("features") {
   if (v8_enable_concurrent_marking) {
     defines += [ "V8_CONCURRENT_MARKING" ]
   }
+  if (v8_enable_lazy_source_positions) {
+    defines += [ "V8_ENABLE_LAZY_SOURCE_POSITIONS" ]
+  }
   if (v8_check_microtasks_scopes_consistency) {
     defines += [ "V8_CHECK_MICROTASKS_SCOPES_CONSISTENCY" ]
   }

src/flags/flag-definitions.h

@@ -295,13 +295,18 @@ DEFINE_BOOL(icu_timezone_data, true, "get information about timezones from ICU")
 #define V8_LITE_BOOL false
 #endif
 
+#ifdef V8_ENABLE_LAZY_SOURCE_POSITIONS
+#define V8_LAZY_SOURCE_POSITIONS_BOOL true
+#else
+#define V8_LAZY_SOURCE_POSITIONS_BOOL false
+#endif
+
 DEFINE_BOOL(lite_mode, V8_LITE_BOOL,
             "enables trade-off of performance for memory savings")
 
 // Lite mode implies other flags to trade-off performance for memory.
 DEFINE_IMPLICATION(lite_mode, jitless)
 DEFINE_IMPLICATION(lite_mode, lazy_feedback_allocation)
-DEFINE_IMPLICATION(lite_mode, enable_lazy_source_positions)
 DEFINE_IMPLICATION(lite_mode, optimize_for_size)
 
 #ifdef V8_ENABLE_FUTURE
@@ -402,7 +407,7 @@ DEFINE_BOOL(ignition_share_named_property_feedback, true,
             "the same object")
 DEFINE_BOOL(print_bytecode, false,
             "print bytecode generated by ignition interpreter")
-DEFINE_BOOL(enable_lazy_source_positions, false,
+DEFINE_BOOL(enable_lazy_source_positions, V8_LAZY_SOURCE_POSITIONS_BOOL,
             "skip generating source positions during initial compile but "
             "regenerate when actually required")
 DEFINE_STRING(print_bytecode_filter, "*",