Remove unnecessary `explicit` qualifiers on constructors.

Change-Id: Id12e392ad50f66a6e2251a68662b7959315dc567
diff --git a/runtime/base/arena_allocator.h b/runtime/base/arena_allocator.h
index c4b36ee..05c66f0 100644
--- a/runtime/base/arena_allocator.h
+++ b/runtime/base/arena_allocator.h
@@ -170,7 +170,7 @@
 
 class MemMapArena FINAL : public Arena {
  public:
-  explicit MemMapArena(size_t size, bool low_4gb);
+  MemMapArena(size_t size, bool low_4gb);
   virtual ~MemMapArena();
   void Release() OVERRIDE;
 
diff --git a/runtime/base/arena_containers.h b/runtime/base/arena_containers.h
index d6c4a54..a7aafdf 100644
--- a/runtime/base/arena_containers.h
+++ b/runtime/base/arena_containers.h
@@ -134,7 +134,7 @@
     typedef ArenaAllocatorAdapter<U> other;
   };
 
-  explicit ArenaAllocatorAdapter(ArenaAllocator* arena_allocator, ArenaAllocKind kind)
+  ArenaAllocatorAdapter(ArenaAllocator* arena_allocator, ArenaAllocKind kind)
       : ArenaAllocatorAdapterKind(kind),
         arena_allocator_(arena_allocator) {
   }
diff --git a/runtime/base/mutex.h b/runtime/base/mutex.h
index 2801fb7..848c904 100644
--- a/runtime/base/mutex.h
+++ b/runtime/base/mutex.h
@@ -437,7 +437,7 @@
 // (Signal) or all at once (Broadcast).
 class ConditionVariable {
  public:
-  explicit ConditionVariable(const char* name, Mutex& mutex);
+  ConditionVariable(const char* name, Mutex& mutex);
   ~ConditionVariable();
 
   void Broadcast(Thread* self);
@@ -475,7 +475,7 @@
 // upon destruction.
 class SCOPED_CAPABILITY MutexLock {
  public:
-  explicit MutexLock(Thread* self, Mutex& mu) ACQUIRE(mu) : self_(self), mu_(mu) {
+  MutexLock(Thread* self, Mutex& mu) ACQUIRE(mu) : self_(self), mu_(mu) {
     mu_.ExclusiveLock(self_);
   }
 
@@ -495,7 +495,7 @@
 // construction and releases it upon destruction.
 class SCOPED_CAPABILITY ReaderMutexLock {
  public:
-  explicit ReaderMutexLock(Thread* self, ReaderWriterMutex& mu) ACQUIRE(mu) :
+  ReaderMutexLock(Thread* self, ReaderWriterMutex& mu) ACQUIRE(mu) :
       self_(self), mu_(mu) {
     mu_.SharedLock(self_);
   }
@@ -517,7 +517,7 @@
 // construction and releases it upon destruction.
 class SCOPED_CAPABILITY WriterMutexLock {
  public:
-  explicit WriterMutexLock(Thread* self, ReaderWriterMutex& mu) EXCLUSIVE_LOCK_FUNCTION(mu) :
+  WriterMutexLock(Thread* self, ReaderWriterMutex& mu) EXCLUSIVE_LOCK_FUNCTION(mu) :
       self_(self), mu_(mu) {
     mu_.ExclusiveLock(self_);
   }
diff --git a/runtime/base/timing_logger.h b/runtime/base/timing_logger.h
index e10cd24..a5344db 100644
--- a/runtime/base/timing_logger.h
+++ b/runtime/base/timing_logger.h
@@ -131,7 +131,7 @@
     friend class TimingLogger;
   };
 
-  explicit TimingLogger(const char* name, bool precise, bool verbose);
+  TimingLogger(const char* name, bool precise, bool verbose);
   ~TimingLogger();
   // Verify that all open timings have related closed timings.
   void Verify();
@@ -156,7 +156,7 @@
   // starts and ends.
   class ScopedTiming {
    public:
-    explicit ScopedTiming(const char* label, TimingLogger* logger) : logger_(logger) {
+    ScopedTiming(const char* label, TimingLogger* logger) : logger_(logger) {
       logger_->StartTiming(label);
     }
     ~ScopedTiming() {
diff --git a/runtime/base/unix_file/fd_file.h b/runtime/base/unix_file/fd_file.h
index d51fbd6..f47368b 100644
--- a/runtime/base/unix_file/fd_file.h
+++ b/runtime/base/unix_file/fd_file.h
@@ -35,8 +35,8 @@
   FdFile();
   // Creates an FdFile using the given file descriptor. Takes ownership of the
   // file descriptor. (Use DisableAutoClose to retain ownership.)
-  explicit FdFile(int fd, bool checkUsage);
-  explicit FdFile(int fd, const std::string& path, bool checkUsage);
+  FdFile(int fd, bool checkUsage);
+  FdFile(int fd, const std::string& path, bool checkUsage);
 
   // Destroys an FdFile, closing the file descriptor if Close hasn't already
   // been called. (If you care about the return value of Close, call it