base: add SmallVector

A vector with inline storage. Falls back on the
heap when exceeding it.

Bug: 205302474
Change-Id: Iaa479ad09dfe7e7c22e41e36e52d3ef1cc1c3706
diff --git a/Android.bp b/Android.bp
index e5fd4a3..cc92485 100644
--- a/Android.bp
+++ b/Android.bp
@@ -6901,6 +6901,7 @@
         "src/base/paged_memory_unittest.cc",
         "src/base/periodic_task_unittest.cc",
         "src/base/scoped_file_unittest.cc",
+        "src/base/small_vector_unittest.cc",
         "src/base/string_splitter_unittest.cc",
         "src/base/string_utils_unittest.cc",
         "src/base/string_view_unittest.cc",