Fix min threshhold calculation for resizing the PDF graphics context

pdf/paint_manager.cc

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "pdf/paint_manager.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "ppapi/c/pp_errors.h"
@@ skipping 23 matching lines @@
   // You can not use a NULL client pointer.
   DCHECK(client);
 }
 
 PaintManager::~PaintManager() {
 }
 
 // static
 pp::Size PaintManager::GetNewContextSize(const pp::Size& current_context_size,
                                          const pp::Size& plugin_size) {
-  // The number of additional space in pixels to allocate to the right/bottom
-  // of the context.
-  const int kBufferSize = 100;
+  // The amount of additional space in pixels to allocate to the right/bottom of
+  // the context.
+  const int kBufferSize = 50;
 
   // Default to returning the same size.
   pp::Size result = current_context_size;
 
-  pp::Size min_size(std::max(current_context_size.width() - kBufferSize, 0),
-                    std::max(current_context_size.height() - kBufferSize, 0));
+  // The minimum size of the plugin before resizing the context to ensure we
+  // aren't wasting too much memory. We deduct twice the kBufferSize from the
+  // current context size which gives a threshhold that is kBufferSize below
+  // the plugin size when the context size was last computed.
+  pp::Size min_size(
+      std::max(current_context_size.width() - 2 * kBufferSize, 0),
+      std::max(current_context_size.height() - 2 * kBufferSize, 0));
+
   // If the plugin size is bigger than the current context size, we need to
   // resize the context. If the plugin size is smaller than the current
   // context size by a given threshhold then resize the context so that we
   // aren't wasting too much memory.
   if (plugin_size.width() > current_context_size.width() ||
       plugin_size.height() > current_context_size.height() ||
       plugin_size.width() < min_size.width() ||
       plugin_size.height() < min_size.height()) {
       // Create a larger context than needed so that if we only resize by a
       // small margin, we don't need a new context.
@@ skipping 224 matching lines @@
   DCHECK(manual_callback_pending_);
   manual_callback_pending_ = false;
 
   // Just because we have a manual callback doesn't mean there are actually any
   // invalid regions. Even though we only schedule this callback when something
   // is pending, a Flush callback could have come in before this callback was
   // executed and that could have cleared the queue.
   if (aggregator_.HasPendingUpdate())
     DoPaint();
 }