MIPS: We should never allocate a 0-sized buffer, so never grow from 0.

Port r22947 (e72b5aed) and r22944 (d1d8f44c)

BUG=
R=paul.lind@imgtec.com

Review URL: https://codereview.chromium.org/446923003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22948 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/assembler-mips.cc

@@ -1974,9 +1974,7 @@ void Assembler::GrowBuffer() {
 
   // Compute new buffer size.
   CodeDesc desc;  // The new buffer.
-  if (buffer_size_ < 4*KB) {
-    desc.buffer_size = 4*KB;
-  } else if (buffer_size_ < 1*MB) {
+  if (buffer_size_ < 1 * MB) {
     desc.buffer_size = 2*buffer_size_;
   } else {
     desc.buffer_size = buffer_size_ + 1*MB;

src/mips64/assembler-mips64.cc

@@ -2631,9 +2631,7 @@ void Assembler::GrowBuffer() {
 
   // Compute new buffer size.
   CodeDesc desc;  // The new buffer.
-  if (buffer_size_ < 4*KB) {
-    desc.buffer_size = 4*KB;
-  } else if (buffer_size_ < 1*MB) {
+  if (buffer_size_ < 1 * MB) {
     desc.buffer_size = 2*buffer_size_;
   } else {
     desc.buffer_size = buffer_size_ + 1*MB;