Remove unused targets_count_ in HeaderChecker

Change-Id: Iff3879d6854555d7ed722717c1dee60537377974
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/21200
Commit-Queue: Takuto Ikuta <tikuta@google.com>
Reviewed-by: David Turner <digit@google.com>
Commit-Queue: David Turner <digit@google.com>

src/gn/header_checker.cc

diff --git a/src/gn/header_checker.cc b/src/gn/header_checker.cc
index a100337..562644d 100644
--- a/src/gn/header_checker.cc
+++ b/src/gn/header_checker.cc
@@ -176,7 +176,6 @@
     : build_settings_(build_settings),
       check_generated_(check_generated),
       check_system_(check_system),
-      targets_count_(targets.size()),
       errors_lock_(),
       task_count_cv_() {
   for (auto* target : targets)

src/gn/header_checker.h

diff --git a/src/gn/header_checker.h b/src/gn/header_checker.h
index 8150bdf..8f36445 100644
--- a/src/gn/header_checker.h
+++ b/src/gn/header_checker.h
@@ -193,8 +193,6 @@
   // execution.
   base::AtomicRefCount task_count_;
 
-  size_t targets_count_ = 0;
-
   // Maps (target_to, target_from) -> is_permitted.
   enum class DependencyState {
     kNotADependency,