Fix google-explicit-constructor warnings in system/core.

* Declare explicit conversion constructors.
* Add NOLINT for implicit conversion constructors.
* Fix also some misaligned indendations.

Bug: 28341362
Change-Id: Idf911f35923b408d92285cc1a053f382ba08c63e
Test: build with clang-tidy
diff --git a/logd/FlushCommand.h b/logd/FlushCommand.h
index 9224773..7172d5f 100644
--- a/logd/FlushCommand.h
+++ b/logd/FlushCommand.h
@@ -35,7 +35,7 @@
     uint64_t mTimeout;
 
 public:
-    FlushCommand(LogReader &mReader,
+    explicit FlushCommand(LogReader &mReader,
                  bool nonBlock = false,
                  unsigned long tail = -1,
                  unsigned int logMask = -1,
diff --git a/logd/LogBuffer.h b/logd/LogBuffer.h
index b390a0c..162c189 100644
--- a/logd/LogBuffer.h
+++ b/logd/LogBuffer.h
@@ -103,7 +103,7 @@
 public:
     LastLogTimes &mTimes;
 
-    LogBuffer(LastLogTimes *times);
+    explicit LogBuffer(LastLogTimes *times);
     void init();
     bool isMonotonic() { return monotonic; }
 
diff --git a/logd/LogCommand.h b/logd/LogCommand.h
index c944478..0adc2a1 100644
--- a/logd/LogCommand.h
+++ b/logd/LogCommand.h
@@ -22,7 +22,7 @@
 
 class LogCommand : public FrameworkCommand {
 public:
-    LogCommand(const char *cmd);
+    explicit LogCommand(const char *cmd);
     virtual ~LogCommand() {}
 };
 
diff --git a/logd/LogReader.h b/logd/LogReader.h
index 98674b8..fdcedf1 100644
--- a/logd/LogReader.h
+++ b/logd/LogReader.h
@@ -27,7 +27,7 @@
     LogBuffer &mLogbuf;
 
 public:
-    LogReader(LogBuffer *logbuf);
+    explicit LogReader(LogBuffer *logbuf);
     void notifyNewLog();
 
     LogBuffer &logbuf(void) const { return mLogbuf; }