MIPS: Adjust default Heap sizes.

This change decreases the default Heap sizes on MIPS (sets the
same sizes as on Android).

Most MIPS hw has smaller RAM size than 700MB, which can lead
to test failures, if a test does not set the  Heap sizes explicitly
(like cctest/test-mark-compact/MarkCompactCollector).

BUG=

Review URL: https://codereview.chromium.org/18447003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15583 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/heap.cc

@@ -74,7 +74,7 @@ Heap::Heap()
 #define LUMP_OF_MEMORY MB
       code_range_size_(0),
 #endif
-#if defined(ANDROID)
+#if defined(ANDROID) || V8_TARGET_ARCH_MIPS
       reserved_semispace_size_(4 * Max(LUMP_OF_MEMORY, Page::kPageSize)),
       max_semispace_size_(4 * Max(LUMP_OF_MEMORY, Page::kPageSize)),
       initial_semispace_size_(Page::kPageSize),