Hookup the generic heap intercept for Windows.

base/allocator/BUILD.gn

Index: base/allocator/BUILD.gn
diff --git a/base/allocator/BUILD.gn b/base/allocator/BUILD.gn
index d25239ae6f849ea320cb44f72ea7c734c7883cd6..7f57e6b2056671ed2ecf6a283b58a3417d5acf44 100644
--- a/base/allocator/BUILD.gn
+++ b/base/allocator/BUILD.gn
@@ -13,8 +13,10 @@ declare_args() {
   enable_debugallocation = is_debug
 }
 
-# Allocator shim is only enabled for Release static builds.
-win_use_allocator_shim = is_win && !is_component_build && !is_debug
+# The Windows-only allocator shim is only enabled for Release static builds, and
+# is mutually exclusive with the generalized shim.
+win_use_allocator_shim = is_win && !is_component_build && !is_debug &&
+                         !use_experimental_allocator_shim
 
 # This "allocator" meta-target will forward to the default allocator according
 # to the build settings.
@@ -38,9 +40,7 @@ group("allocator") {
 # assumes that the library using it will eventually be linked with
 # //base/allocator in the default way. Clean this up and delete this.
 config("allocator_shim_define") {
-  if (win_use_allocator_shim) {
-    defines = [ "ALLOCATOR_SHIM" ]
-  }
+  defines = [ "ALLOCATOR_SHIM" ]

[Primiano Tucci (use gerrit), 2016/07/12 14:51:04]

If I am understanding this correctly you are dropping this if so you can recycle
the define for the tests.
See my proposal on the top, let's have a different define for the tests, in the
allocator features buildflag header.

[Sigurður Ásgeirsson, 2016/07/14 19:04:26]

Done.

 }
 
 config("tcmalloc_flags") {
@@ -79,6 +79,8 @@ config("tcmalloc_flags") {
 if (win_use_allocator_shim) {
   source_set("allocator_shim") {
     sources = [
+      "allocator_impl_win.cc",

[Primiano Tucci (use gerrit), 2016/07/12 14:51:04]

I think just for the sake of making all these files less obscure this should
have winheap in the name. 
Maybe: winheap_stubs_win.h/cc ? or something similar

[Sigurður Ásgeirsson, 2016/07/14 19:04:26]

Done.

+      "allocator_impl_win.h",
       "allocator_shim_win.cc",
       "allocator_shim_win.h",
     ]
@@ -302,7 +304,18 @@ if (use_experimental_allocator_shim) {
       "allocator_shim_override_cpp_symbols.h",
       "allocator_shim_override_libc_symbols.h",
     ]
-    if (is_linux && use_allocator == "tcmalloc") {
+    if (is_win) {
+      sources += [
+        "allocator_impl_win.cc",
+        "allocator_impl_win.h",
+      ]
+
+      # This gates tests that require the presence of the allocator shim.
+      configs += [ ":allocator_shim_define" ]

[Primiano Tucci (use gerrit), 2016/07/12 14:51:04]

if you follow my suggestion above about having the
ENABLE_WIN_ALLOCATOR_SHIM_TESTS in the features there is not need for this line,
as the allocator features are already a dep of base.

[Sigurður Ásgeirsson, 2016/07/14 19:04:26]

Done.

+    }
+    if (is_win) {
+      sources += [ "allocator_shim_default_dispatch_to_winheap.cc" ]
+    } else if (is_linux && use_allocator == "tcmalloc") {
       sources += [
         "allocator_shim_default_dispatch_to_tcmalloc.cc",
         "allocator_shim_override_glibc_weak_symbols.h",