Memory improvements to render_pdfs; better DM pool size defaults

src/lazy/SkDiscardableMemoryPool.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkDiscardableMemoryPool_DEFINED
 #define SkDiscardableMemoryPool_DEFINED
 
@@ skipping 44 matching lines @@
             size_t size, SkBaseMutex* mutex = NULL);
 };
 
 /**
  *  Returns (and creates if needed) a threadsafe global
  *  SkDiscardableMemoryPool.
  */
 SkDiscardableMemoryPool* SkGetGlobalDiscardableMemoryPool();
 
 #if !defined(SK_DEFAULT_GLOBAL_DISCARDABLE_MEMORY_POOL_SIZE)
-#define SK_DEFAULT_GLOBAL_DISCARDABLE_MEMORY_POOL_SIZE (128 * 1024 * 1024)
+    #if defined(SK_DEFAULT_RESOURCE_CACHE_MB_LIMIT) && \
+            SK_DEFAULT_RESOURCE_CACHE_MB_LIMIT > 0
+        #define SK_DEFAULT_GLOBAL_DISCARDABLE_MEMORY_POOL_SIZE \
+                (SK_DEFAULT_RESOURCE_CACHE_MB_LIMIT * 1024 * 1024)
+    #else
+        #ifdef SK_BUILD_FOR_ANDROID
+            #define SK_DEFAULT_GLOBAL_DISCARDABLE_MEMORY_POOL_SIZE \
+                    (64 * 1024 * 1024)
+        #else
+            #define SK_DEFAULT_GLOBAL_DISCARDABLE_MEMORY_POOL_SIZE \
+                    (128 * 1024 * 1024)
+        #endif
+    #endif
 #endif
 
 #endif  // SkDiscardableMemoryPool_DEFINED