base: Change DCHECK_IS_ON to a macro DCHECK_IS_ON().

This ensures that if the header is not included, and a DCHECK is guarded
by this check, that the file will fail to compile instead of silently
compiling the DCHECK out.

For example:

#if DCHECK_IS_ON
DCHECK(SomeThing());
#endif

This example would be compiled out if DCHECK_IS_ON was not defined due
to not including the logging.h header.

Instead, this will fail to compile:

#if DCHECK_IS_ON()
DCHECK(SomeThing());
#endif

R=thakis@chromium.org

Review URL: https://codereview.chromium.org/842523002

Cr-Commit-Position: refs/heads/master@{#310626}

2 files changed, 6 insertions, 6 deletions

diff --git a/base/memory/discardable_shared_memory.cc b/base/memory/discardable_shared_memory.cc
index 82bc983..e04377e 100644
--- a/base/memory/discardable_shared_memory.cc
+++ b/base/memory/discardable_shared_memory.cc
@@ -129,7 +129,7 @@ bool DiscardableSharedMemory::CreateAndMap(size_t size) {
       shared_memory_.mapped_size() - AlignToPageSize(sizeof(SharedState));
 
   locked_page_count_ = AlignToPageSize(mapped_size_) / base::GetPageSize();
-#if DCHECK_IS_ON
+#if DCHECK_IS_ON()
   for (size_t page = 0; page < locked_page_count_; ++page)
     locked_pages_.insert(page);
 #endif
@@ -149,7 +149,7 @@ bool DiscardableSharedMemory::Map(size_t size) {
       shared_memory_.mapped_size() - AlignToPageSize(sizeof(SharedState));
 
   locked_page_count_ = AlignToPageSize(mapped_size_) / base::GetPageSize();
-#if DCHECK_IS_ON
+#if DCHECK_IS_ON()
   for (size_t page = 0; page < locked_page_count_; ++page)
     locked_pages_.insert(page);
 #endif
@@ -200,7 +200,7 @@ bool DiscardableSharedMemory::Lock(size_t offset, size_t length) {
   // Add pages to |locked_page_count_|.
   // Note: Locking a page that is already locked is an error.
   locked_page_count_ += end - start;
-#if DCHECK_IS_ON
+#if DCHECK_IS_ON()
   // Detect incorrect usage by keeping track of exactly what pages are locked.
   for (auto page = start; page < end; ++page) {
     auto result = locked_pages_.insert(page);
@@ -252,7 +252,7 @@ void DiscardableSharedMemory::Unlock(size_t offset, size_t length) {
   // Note: Unlocking a page that is not locked is an error.
   DCHECK_GE(locked_page_count_, end - start);
   locked_page_count_ -= end - start;
-#if DCHECK_IS_ON
+#if DCHECK_IS_ON()
   // Detect incorrect usage by keeping track of exactly what pages are locked.
   for (auto page = start; page < end; ++page) {
     auto erased_count = locked_pages_.erase(page);
diff --git a/base/memory/discardable_shared_memory.h b/base/memory/discardable_shared_memory.h
index c69c970..abee868 100644
--- a/base/memory/discardable_shared_memory.h
+++ b/base/memory/discardable_shared_memory.h
@@ -11,7 +11,7 @@
 #include "base/threading/thread_collision_warner.h"
 #include "base/time/time.h"
 
-#if DCHECK_IS_ON
+#if DCHECK_IS_ON()
 #include <set>
 #endif
 
@@ -119,7 +119,7 @@ class BASE_EXPORT DiscardableSharedMemory {
   SharedMemory shared_memory_;
   size_t mapped_size_;
   size_t locked_page_count_;
-#if DCHECK_IS_ON
+#if DCHECK_IS_ON()
   std::set<size_t> locked_pages_;
 #endif
   // Implementation is not thread-safe but still usable if clients are