Fix AnimationParser remove_prefix test

The test fails because TEST_STRING, a char[], is silently
converted to a std::string, passed to remove_prefix, then
the string is destroyed, but a pointer to the string is
returned.

Fix it by changing the signature of remove_prefix to use
std::string_view to be more robust in handling raw char*.

Test: run it
Change-Id: I553c066907f09cf330c8b7a4659db5a1fee82cac
diff --git a/healthd/AnimationParser.h b/healthd/AnimationParser.h
index bc00845..f55b563 100644
--- a/healthd/AnimationParser.h
+++ b/healthd/AnimationParser.h
@@ -17,6 +17,8 @@
 #ifndef HEALTHD_ANIMATION_PARSER_H
 #define HEALTHD_ANIMATION_PARSER_H
 
+#include <string_view>
+
 #include "animation.h"
 
 namespace android {
@@ -24,7 +26,7 @@
 bool parse_animation_desc(const std::string& content, animation* anim);
 
 bool can_ignore_line(const char* str);
-bool remove_prefix(const std::string& str, const char* prefix, const char** rest);
+bool remove_prefix(std::string_view str, const char* prefix, const char** rest);
 bool parse_text_field(const char* in, animation::text_field* field);
 }  // namespace android