Create base::win::MemoryPressureMonitor class.

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index e7985ef47311ce2be7ee27377aba78b2992d35c4..dc3a737937ea1e0126b601da8415ad595dd4026f 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -599,6 +599,8 @@ component("base") {
     "win/iat_patch_function.h",
     "win/iunknown_impl.cc",
     "win/iunknown_impl.h",
+    "win/memory_pressure_monitor.cc",

[Nico, 2015/05/05 21:25:11]

can you call this memory_pressure_monitor_win for consistency with cros and mac?

[chrisha, 2015/05/06 02:40:24]

I originally had that, but removed it at grt@'s request. I'm all for
consistency, and can fix the others while I'm at it. grt@ is arguing that it's
redundant, given that it's in a 'win' specific directory and namespace. Your
opinion? 

[grt (UTC plus 2), 2015/05/06 13:26:36]

We use the base::win namespace for files in src/base/win, so I think putting
"Win" in the file/class name isn't needed. After I left the comments about this
I noticed that the other implementations of the monitor had the platform name in
them. I see the "consistency with the other monitors" sentiment, but I
personally prefer consistency with the rest of base/win.

[Nico, 2015/05/06 22:57:14]

On Mac, it's also the only file named _mac. I'm fine with renaming the existing
other two files to not have the suffix, but it should be consistent

+    "win/memory_pressure_monitor.h",
     "win/message_window.cc",
     "win/message_window.h",
     "win/metro.cc",
@@ -1282,6 +1284,7 @@ test("base_unittests") {
     "win/event_trace_provider_unittest.cc",
     "win/i18n_unittest.cc",
     "win/iunknown_impl_unittest.cc",
+    "win/memory_pressure_monitor_unittest.cc",
     "win/message_window_unittest.cc",
     "win/object_watcher_unittest.cc",
     "win/pe_image_unittest.cc",