fixing bug in 2D context painted area pixel count computation ...

chrome/renderer/webplugin_delegate_pepper.cc

Index: chrome/renderer/webplugin_delegate_pepper.cc
===================================================================
--- chrome/renderer/webplugin_delegate_pepper.cc	(revision 43985)
+++ chrome/renderer/webplugin_delegate_pepper.cc	(working copy)
@@ -480,9 +480,11 @@
   } else if (state == NPExtensionsReservedStateSharedMemoryChecksum) {
     if (!context)
       return NPERR_INVALID_PARAM;
-    int32 row_count = context->dirty.bottom - context->dirty.top + 1;
-    int32 stride = context->dirty.right - context->dirty.left + 1;
-    size_t length = row_count * stride * sizeof(uint32);
+    // Bytes per pixel.
+    static const int kBytesPixel = 4;
+    int32 row_count = context->dirty.bottom - context->dirty.top;
+    int32 stride = context->dirty.right - context->dirty.left;
+    size_t length = row_count * stride * kBytesPixel;
     MD5Digest md5_result;   // 128-bit digest
     MD5Sum(context->region, length, &md5_result);
     std::string hex_md5 = MD5DigestToBase16(md5_result);