Bug 1400754 - stylo: crash on Win64 Asan build. r=manishearth, dmajor.

* adds a hashglobe::alloc::realloc, as that was previously not implemented,
  copying and simplifying from liballoc_system.

* routes malloc and realloc calls through hashglobe::alloc::, instead of
  doing it via direct 'extern "C"' calls.

components/fallible/lib.rs

@@ -6,16 +6,12 @@ extern crate hashglobe;
 extern crate smallvec;
 
 use hashglobe::FailedAllocationError;
+#[cfg(feature = "known_system_malloc")]
+use hashglobe::alloc;
 use smallvec::Array;
 use smallvec::SmallVec;
 use std::vec::Vec;
 
-#[cfg(feature = "known_system_malloc")]
-extern "C" {
-    fn realloc(ptr: *mut u8, bytes: usize) -> *mut u8;
-    fn malloc(bytes: usize) -> *mut u8;
-}
-
 pub trait FallibleVec<T> {
     /// Append |val| to the end of |vec|.  Returns Ok(()) on success,
     /// Err(reason) if it fails, with |reason| describing the failure.
@@ -67,9 +63,9 @@ fn try_double_vec<T>(vec: &mut Vec<T>) -> Result<(), FailedAllocationError> {
 
     let new_ptr = unsafe {
         if old_cap == 0 {
-            malloc(new_size_bytes)
+            alloc::alloc(new_size_bytes, 0)
         } else {
-            realloc(old_ptr as *mut u8, new_size_bytes)
+            alloc::realloc(old_ptr as *mut u8, new_size_bytes)
         }
     };
 
@@ -146,12 +142,12 @@ where
         // There's an old block to free, and, presumably, old contents to
         // copy.  realloc takes care of both aspects.
         unsafe {
-            new_ptr = realloc(old_ptr as *mut u8, new_size_bytes);
+            new_ptr = alloc::realloc(old_ptr as *mut u8, new_size_bytes);
         }
     } else {
         // There's no old block to free.  There may be old contents to copy.
         unsafe {
-            new_ptr = malloc(new_size_bytes);
+            new_ptr = alloc::alloc(new_size_bytes, 0);
             if !new_ptr.is_null() && old_size_bytes > 0 {
                 copy_nonoverlapping(old_ptr as *const u8,
                                     new_ptr as *mut u8, old_size_bytes);