Empty implementations for SkImageDecoder.

Add constructor and destructor, so SkScaledBitmapSampler's
DummyDecoder has no unresolved symbols in Chrome.

Fixes our Chrome canary.

Unreviewed.

Review URL: https://codereview.chromium.org/25536004

git-svn-id: http://skia.googlecode.com/svn/trunk@11566 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/ports/SkImageDecoder_empty.cpp b/src/ports/SkImageDecoder_empty.cpp
index 69e6ec9..ff2fa02 100644
--- a/src/ports/SkImageDecoder_empty.cpp
+++ b/src/ports/SkImageDecoder_empty.cpp
@@ -19,6 +19,10 @@
 
 // Empty implementations for SkImageDecoder.
 
+SkImageDecoder::SkImageDecoder() {}
+
+SkImageDecoder::~SkImageDecoder() {}
+
 SkImageDecoder* SkImageDecoder::Factory(SkStreamRewindable*) {
     return NULL;
 }