applypatch: Change the patch parameter to const Value& in Apply{BSDiff,Image}Patch.

It used to be "const Value*", but nullptr won't be a valid input.

Test: recovery_host_test; recovery_component_test
Change-Id: I904b5689ac3e64504088bf0544c9fb5d45a52243

applypatch/include/applypatch/applypatch.h

@@ -45,6 +45,7 @@ extern std::string cache_temp_source;
 using SinkFn = std::function<size_t(const unsigned char*, size_t)>;
 
 // applypatch.cpp
+
 int ShowLicenses();
 size_t FreeSpaceForFile(const char* filename);
 int CacheSizeCheck(size_t bytes);
@@ -66,15 +67,25 @@ int LoadFileContents(const char* filename, FileContents* file);
 int SaveFileContents(const char* filename, const FileContents* file);
 
 // bspatch.cpp
+
 void ShowBSDiffLicense();
-int ApplyBSDiffPatch(const unsigned char* old_data, size_t old_size, const Value* patch,
+
+// Applies the bsdiff-patch given in 'patch' (from offset 'patch_offset' to the end) to the source
+// data given by (old_data, old_size). Writes the patched output through the given 'sink', and
+// updates the SHA-1 context with the output data. Returns 0 on success.
+int ApplyBSDiffPatch(const unsigned char* old_data, size_t old_size, const Value& patch,
                      size_t patch_offset, SinkFn sink, SHA_CTX* ctx);
 
 // imgpatch.cpp
-int ApplyImagePatch(const unsigned char* old_data, size_t old_size, const Value* patch, SinkFn sink,
+
+// Applies the imgdiff-patch given in 'patch' to the source data given by (old_data, old_size), with
+// the optional bonus data. Writes the patched output through the given 'sink', and updates the
+// SHA-1 context with the output data. Returns 0 on success.
+int ApplyImagePatch(const unsigned char* old_data, size_t old_size, const Value& patch, SinkFn sink,
                     SHA_CTX* ctx, const Value* bonus_data);
 
 // freecache.cpp
+
 int MakeFreeSpaceOnCache(size_t bytes_needed);
 
 #endif