Modifed platform bitmap to support win32k lockdown.

This patch detects if the current process is under win32k lockdown
and instead of using the GDI route it maps the shared section directly.
This is done for supporting the introduction of win32k lockdown for
PPAPI processes. To minimize the chances of disruption when not under
win32k lockdown the code path is kept the same.

BUG=523278

Review URL: https://codereview.chromium.org/1321913002

Cr-Commit-Position: refs/heads/master@{#350828}

skia/ext/bitmap_platform_device_win.cc

@@ -7,6 +7,7 @@
 
 #include "base/debug/gdi_debug_util_win.h"
 #include "base/logging.h"
+#include "base/win/win_util.h"
 #include "skia/ext/bitmap_platform_device_win.h"
 #include "skia/ext/platform_canvas.h"
 #include "third_party/skia/include/core/SkMatrix.h"
@@ -108,7 +109,12 @@ void BitmapPlatformDevice::LoadConfig() {
 }
 
 static void DeleteHBitmapCallback(void* addr, void* context) {
-  DeleteObject(static_cast<HBITMAP>(context));
+  // If context is not NULL then it's a valid HBITMAP to delete.
+  // Otherwise we just unmap the pixel memory.
+  if (context)
+    DeleteObject(static_cast<HBITMAP>(context));
+  else
+    UnmapViewOfFile(addr);
 }
 
 static bool InstallHBitmapPixels(SkBitmap* bitmap, int width, int height,
@@ -133,10 +139,25 @@ BitmapPlatformDevice* BitmapPlatformDevice::Create(
     bool do_clear) {
 
   void* data;
-  HBITMAP hbitmap = CreateHBitmap(width, height, is_opaque, shared_section,
-                                  &data);
-  if (!hbitmap)
-    return NULL;
+  HBITMAP hbitmap = NULL;
+
+  // This function contains an implementation of a Skia platform bitmap for
+  // drawing and compositing graphics. The original implementation uses Windows
+  // GDI to create the backing bitmap memory, however it's possible for a
+  // process to not have access to GDI which will cause this code to fail. It's
+  // possible to detect when GDI is unavailable and instead directly map the
+  // shared memory as the bitmap.
+  if (base::win::IsUser32AndGdi32Available()) {
+    hbitmap = CreateHBitmap(width, height, is_opaque, shared_section, &data);
+    if (!hbitmap)
+      return NULL;
+  } else {
+    DCHECK(shared_section != NULL);
+    data = MapViewOfFile(shared_section, FILE_MAP_WRITE, 0, 0,
+                         PlatformCanvasStrideForWidth(width) * height);
+    if (!data)
+      return NULL;
+  }
 
   SkBitmap bitmap;
   if (!InstallHBitmapPixels(&bitmap, width, height, is_opaque, data, hbitmap))
@@ -179,13 +200,15 @@ BitmapPlatformDevice::BitmapPlatformDevice(
       transform_(SkMatrix::I()) {
   // The data object is already ref'ed for us by create().
   SkDEBUGCODE(begin_paint_count_ = 0);
-  SetPlatformDevice(this, this);
-  // Initialize the clip region to the entire bitmap.
-  BITMAP bitmap_data;
-  if (GetObject(hbitmap_, sizeof(BITMAP), &bitmap_data)) {
-    SkIRect rect;
-    rect.set(0, 0, bitmap_data.bmWidth, bitmap_data.bmHeight);
-    clip_region_ = SkRegion(rect);
+  if (hbitmap) {
+    SetPlatformDevice(this, this);
+    // Initialize the clip region to the entire bitmap.
+    BITMAP bitmap_data;
+    if (GetObject(hbitmap_, sizeof(BITMAP), &bitmap_data)) {
+      SkIRect rect;
+      rect.set(0, 0, bitmap_data.bmWidth, bitmap_data.bmHeight);
+      clip_region_ = SkRegion(rect);
+    }
   }
 }