[heap] Make --trace-gc-verbose imply --trace-gc

Change-Id: I428149f7e9b462bf75187ae0e10115a663579e43
Reviewed-on: https://chromium-review.googlesource.com/c/1425522Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58974}

src/flag-definitions.h

@@ -693,6 +693,8 @@ DEFINE_BOOL(trace_idle_notification_verbose, false,
             "prints the heap state used by the idle notification")
 DEFINE_BOOL(trace_gc_verbose, false,
             "print more details following each garbage collection")
+DEFINE_IMPLICATION(trace_gc_verbose, trace_gc)
+
 DEFINE_INT(trace_allocation_stack_interval, -1,
            "print stack trace after <n> free-list allocations")
 DEFINE_INT(trace_duplicate_threshold_kb, 0,