Fix ASharedMemory doxygen formatting, add availability.

Bug: N/A
Test: ran doxygen locally
Change-Id: Ia9924a719a79852a809d4c9989960e19931c4f5e
diff --git a/include/android/sharedmem.h b/include/android/sharedmem.h
index 46d2f4b..107de64 100644
--- a/include/android/sharedmem.h
+++ b/include/android/sharedmem.h
@@ -21,6 +21,7 @@
 
 /**
  * @file sharedmem.h
+ * @brief Shared memory buffers that can be shared across process.
  */
 
 #ifndef ANDROID_SHARED_MEMORY_H
@@ -44,10 +45,6 @@
  *   - DO NOT CHANGE THE LAYOUT OR SIZE OF STRUCTURES
  */
 
-/**
- * Structures and functions for a shared memory buffer that can be shared across process.
- */
-
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -63,6 +60,8 @@
  *
  * Use close() to release the shared memory region.
  *
+ * Available since API level 26.
+ *
  * \param name an optional name.
  * \param size size of the shared memory region
  * \return file descriptor that denotes the shared memory; error code on failure.
@@ -72,6 +71,8 @@
 /**
  * Get the size of the shared memory region.
  *
+ * Available since API level 26.
+ *
  * \param fd file descriptor of the shared memory region
  * \return size in bytes; 0 if fd is not a valid shared memory file descriptor.
  */
@@ -101,6 +102,8 @@
  *
  *     // share fd with another process here and the other process can only map with PROT_READ.
  *
+ * Available since API level 26.
+ *
  * \param fd   file descriptor of the shared memory region.
  * \param prot any bitwise-or'ed combination of PROT_READ, PROT_WRITE, PROT_EXEC denoting
  *             updated access. Note access can only be removed, but not added back.
diff --git a/include/android/sharedmem_jni.h b/include/android/sharedmem_jni.h
index 85ac78f..2af3955 100644
--- a/include/android/sharedmem_jni.h
+++ b/include/android/sharedmem_jni.h
@@ -21,6 +21,7 @@
 
 /**
  * @file sharedmem_jni.h
+ * @brief Shared memory buffers that can be shared across process.
  */
 
 #ifndef ANDROID_SHARED_MEMORY_JNI_H
@@ -46,10 +47,6 @@
  *   - DO NOT CHANGE THE LAYOUT OR SIZE OF STRUCTURES
  */
 
-/**
- * Structures and functions for a shared memory buffer that can be shared across process.
- */
-
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -64,6 +61,8 @@
  *
  * Use close() to release the shared memory region.
  *
+ * Available since API level 27.
+ *
  * \param env The JNIEnv* pointer
  * \param sharedMemory The Java android.os.SharedMemory object
  * \return file descriptor that denotes the shared memory; -1 if the shared memory object is