linux_aura: Fix PRIMARY selection in the content area.

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index 6467e701bf5dea13360764139ee008f17a50d8ca..33fc7e764fdcb302ab1b89d125f379352c057e96 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -1041,12 +1041,20 @@ void RenderWidgetHostViewAura::SelectionChanged(const base::string16& text,
 #if defined(USE_X11) && !defined(OS_CHROMEOS)
   if (text.empty() || range.is_empty())
     return;
+  size_t pos = range.GetMin() - offset;
+  size_t n = range.length();
+
+  DCHECK(pos + n <= text.length()) << "The text can not fully cover range.";
+  if (pos >= text.length()) {
+    NOTREACHED() << "The text can not cover range.";
+    return;
+  }
 
   // Set the CLIPBOARD_TYPE_SELECTION to the ui::Clipboard.
   ui::ScopedClipboardWriter clipboard_writer(
       ui::Clipboard::GetForCurrentThread(),
       ui::CLIPBOARD_TYPE_SELECTION);
-  clipboard_writer.WriteText(text);
+  clipboard_writer.WriteText(text.substr(pos, n));
 #endif  // defined(USE_X11) && !defined(OS_CHROMEOS)
 }