Suppress implicit-fallthrough warnings.

Add FALLTHROUGH_INTENDED for clang compiler.

Bug: 112564944
Test: build with global -Wimplicit-fallthrough.
Change-Id: I40f8bbf94e207c9dd90921e9b762ba51abab5777
diff --git a/libutils/Android.bp b/libutils/Android.bp
index 1c1bdf7..600c91c 100644
--- a/libutils/Android.bp
+++ b/libutils/Android.bp
@@ -59,6 +59,7 @@
         "-Werror",
     ],
     header_libs: [
+        "libbase_headers",
         "libutils_headers",
     ],
     export_header_lib_headers: [
diff --git a/libutils/RefBase.cpp b/libutils/RefBase.cpp
index 3f1e79a..ae10789 100644
--- a/libutils/RefBase.cpp
+++ b/libutils/RefBase.cpp
@@ -19,6 +19,8 @@
 
 #include <memory>
 
+#include <android-base/macros.h>
+
 #include <utils/RefBase.h>
 
 #include <utils/CallStack.h>
@@ -479,7 +481,7 @@
     case INITIAL_STRONG_VALUE:
         refs->mStrong.fetch_sub(INITIAL_STRONG_VALUE,
                 std::memory_order_relaxed);
-        // fall through...
+        FALLTHROUGH_INTENDED;
     case 0:
         refs->mBase->onFirstRef();
     }
diff --git a/libutils/Unicode.cpp b/libutils/Unicode.cpp
index 82f650d..5f0a51f 100644
--- a/libutils/Unicode.cpp
+++ b/libutils/Unicode.cpp
@@ -16,8 +16,9 @@
 
 #define LOG_TAG "unicode"
 
-#include <utils/Unicode.h>
+#include <android-base/macros.h>
 #include <limits.h>
+#include <utils/Unicode.h>
 
 #include <log/log.h>
 
@@ -105,8 +106,11 @@
     switch (bytes)
     {   /* note: everything falls through. */
         case 4: *--dstP = (uint8_t)((srcChar | kByteMark) & kByteMask); srcChar >>= 6;
+            FALLTHROUGH_INTENDED;
         case 3: *--dstP = (uint8_t)((srcChar | kByteMark) & kByteMask); srcChar >>= 6;
+            FALLTHROUGH_INTENDED;
         case 2: *--dstP = (uint8_t)((srcChar | kByteMark) & kByteMask); srcChar >>= 6;
+            FALLTHROUGH_INTENDED;
         case 1: *--dstP = (uint8_t)(srcChar | kFirstByteMark[bytes]);
     }
 }