Branch the files in the shim layer that switches between the...

base/allocator/README

-Notes about the Chrome port of tcmalloc & jemalloc.
+Notes about the Chrome memory allocator.
 
 Background
 ----------
 We use this library as a generic way to fork into any of several allocators.
 Currently we can, at runtime, switch between:
    the default windows allocator
    the windows low-fragmentation-heap
    tcmalloc
    jemalloc (the heap used most notably within Mozilla Firefox)
 
 The mechanism for hooking LIBCMT in windows is rather tricky.  The core
 problem is that by default, the windows library does not declare malloc and
 free as weak symbols.  Because of this, they cannot be overriden.  To work
 around this, we start with the LIBCMT.LIB, and manually remove all allocator
 related functions from it using the visual studio library tool.  Once removed,
 we can now link against the library and provide custom versions of the 
 allocator related functionality.
 
 
 Source code
 -----------
-Everything within the directory tcmalloc/tcmalloc is pulled directly from the
-google-perftools repository.  For the most part, tcmalloc is a stock build
-from there.
+This directory contains just the allocator (i.e. shim) layer that switches
+between the different underlying memory allocation implementations.
 
-We have forked a few files.  We always push our changes upstream, so over
-time the forked files should disappear.  Currently forked files include:
-   page_heap.cc
-   port.cc
-   system-alloc.cc
-   system-alloc.h
-   tcmalloc.cc
+The tcmalloc and jemalloc libraries originate outside of Chromium
+and exist in ../../third_party/tcmalloc and ../../third_party/jemalloc
+(currently, the actual locations are defined in the allocator.gyp file).
+The third party sources use a vendor-branch SCM pattern to track
+Chromium-specific changes independently from upstream changes.
 
+The general intent is to push local changes upstream so that over
+time we no longer need any forked files.
+
+
+Adding a new allocator
+----------------------
 Adding a new allocator requires definition of the following five functions:
+
   extern "C" {
     bool init();
     void* malloc(size_t s);
     void* realloc(void* p, size_t s);
     void free(void* s);
     size_t msize(void* p);
   }
 
 All other allocation related functions (new/delete/calloc/etc) have been
 implemented generically to work across all allocators.
 
 
 Usage
 -----
 You can use the different allocators by setting the environment variable
 CHROME_ALLOCATOR to:
    "tcmalloc"  - TC Malloc (default)
    "jemalloc"  - JE Malloc
    "winheap"   - Windows default heap
    "winlfh"    - Windows Low-Fragmentation heap
-
-
-Local modifications
--------------------
-jemalloc has been modified slightly to work within the Chromium build.