Fix a crash when saving a <canvas> or <img> image which is large.

content/common/content_constants_internal.cc

Index: content/common/content_constants_internal.cc
diff --git a/content/common/content_constants_internal.cc b/content/common/content_constants_internal.cc
index f5da70e3eefffafebf3db691ea77fe76938f3a4f..8703f80364c86a4f8526b977646b1c858bed2db4 100644
--- a/content/common/content_constants_internal.cc
+++ b/content/common/content_constants_internal.cc
@@ -12,6 +12,9 @@ const uint16 kMaxPluginSideLength = 1 << 15;
 // 8m pixels.
 const uint32 kMaxPluginSize = 8 << 20;
 
+// 10MiB
+const size_t kMaxLengthOfDataURLString = 1024 * 1024 * 10;
+
 const int kTraceEventBrowserProcessSortIndex = -6;
 const int kTraceEventRendererProcessSortIndex = -5;
 const int kTraceEventPluginProcessSortIndex = -4;