Extended Android file store error logs.

[ Merge of http://go/wvgerrit/120763 ]

This change introduces additional logging information for files and
file system operations on Android.

File reading and writing will attempt to make sense of |errno| and
log useful information.   In the event that the file must be closed,
the file stat will be printed.

Failures in determining the file size will print potential reasons for
the encountered error.

This partly restructures the File interface implementation to use file
descriptors instead of the C standard libraries FILE handle.  This is
done to ensure that |errno| is set to an expected value.

This change also introduces the utility functions SafeWrite() and
SafeRead() to handle common, retriable errors.

Bug: 178232354
Test: Android MediaDrm GTS and Android file-based unittests
Change-Id: I15a3c47a271098c9edb4bd9f619ed1a12dca6143

libwvdrmengine/cdm/util/include/file_utils.h

@@ -13,7 +13,7 @@ const char kCurrentDirectory[] = ".";
 const char kParentDirectory[] = "..";
 const char kDirectoryDelimiter = '/';
 const char kWildcard[] = "*";
-bool IsCurrentOrParentDirectory(char* dir);
+bool IsCurrentOrParentDirectory(const char* dir);
 
 class FileUtils {
  public: