Memory improvements to render_pdfs; better DM pool size defaults

src/lazy/SkDiscardableMemoryPool.h

Index: src/lazy/SkDiscardableMemoryPool.h
diff --git a/src/lazy/SkDiscardableMemoryPool.h b/src/lazy/SkDiscardableMemoryPool.h
index d141507004151360931df09b8622862dc480962b..6f528782b9e87d1e2e1ca112ec61869d8c24ecd3 100644
--- a/src/lazy/SkDiscardableMemoryPool.h
+++ b/src/lazy/SkDiscardableMemoryPool.h
@@ -62,7 +62,19 @@ public:
 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