[base] Make MappedFile work with OS file handles

adb uses its own implementation of Windows HANDLE->int mapping,
and it doesn't play well with _get_osfhandle() function used in
MappedFile::FromFd().

This CL adds another function that accepts raw handle, so adb
can pass it directly

+ make constant functions 'const'
+ make the MappedFile movable, as nothing prevents it from being
  one

Test: libbase_test

Change-Id: Ifde4a4094b910e9c7b431126ecf3fef5aa3bb4a6

1 files changed, 4 insertions, 1 deletions

diff --git a/base/mapped_file_test.cpp b/base/mapped_file_test.cpp
index cfde73c74..3629108c9 100644
--- a/base/mapped_file_test.cpp
+++ b/base/mapped_file_test.cpp
@@ -44,5 +44,8 @@ TEST(mapped_file, zero_length_mapping) {
   ASSERT_TRUE(tf.fd != -1);
 
   auto m = android::base::MappedFile::FromFd(tf.fd, 4096, 0, PROT_READ);
-  ASSERT_EQ(0u, m->size());
+  ASSERT_NE(nullptr, m);
+  EXPECT_TRUE((bool)*m);
+  EXPECT_EQ(0u, m->size());
+  EXPECT_NE(nullptr, m->data());
 }