Fix thumbnail store crashing on loading old files

- Was loading thumbnails in little endian, but since the files were from java's
output stream they were in big endian.  This was causing all sorts of issues
with old thumbnails.
- Added back ETC1 header and fixed the file format to match the old version.

BUG=398319

Review URL: https://codereview.chromium.org/486093002

Cr-Commit-Position: refs/heads/master@{#290708}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@290708 0039d316-1c4b-4281-b951-d872f2087c98

third_party/android_opengl/etc1/etc1.cpp

@@ -587,3 +587,63 @@ bool etc1_encode_image(const etc1_byte* pIn, etc1_uint32 width, etc1_uint32 heig
     }
     return true;
 }
+
+static const char kMagic[] = { 'P', 'K', 'M', ' ', '1', '0' };
+
+static const etc1_uint32 ETC1_PKM_FORMAT_OFFSET = 6;
+static const etc1_uint32 ETC1_PKM_ENCODED_WIDTH_OFFSET = 8;
+static const etc1_uint32 ETC1_PKM_ENCODED_HEIGHT_OFFSET = 10;
+static const etc1_uint32 ETC1_PKM_WIDTH_OFFSET = 12;
+static const etc1_uint32 ETC1_PKM_HEIGHT_OFFSET = 14;
+
+static const etc1_uint32 ETC1_RGB_NO_MIPMAPS = 0;
+
+static void writeBEUint16(etc1_byte* pOut, etc1_uint32 data) {
+    pOut[0] = (etc1_byte) (data >> 8);
+    pOut[1] = (etc1_byte) data;
+}
+
+static etc1_uint32 readBEUint16(const etc1_byte* pIn) {
+    return (pIn[0] << 8) | pIn[1];
+}
+
+// Format a PKM header
+
+void etc1_pkm_format_header(etc1_byte* pHeader, etc1_uint32 width, etc1_uint32 height) {
+    memcpy(pHeader, kMagic, sizeof(kMagic));
+    etc1_uint32 encodedWidth = (width + 3) & ~3;
+    etc1_uint32 encodedHeight = (height + 3) & ~3;
+    writeBEUint16(pHeader + ETC1_PKM_FORMAT_OFFSET, ETC1_RGB_NO_MIPMAPS);
+    writeBEUint16(pHeader + ETC1_PKM_ENCODED_WIDTH_OFFSET, encodedWidth);
+    writeBEUint16(pHeader + ETC1_PKM_ENCODED_HEIGHT_OFFSET, encodedHeight);
+    writeBEUint16(pHeader + ETC1_PKM_WIDTH_OFFSET, width);
+    writeBEUint16(pHeader + ETC1_PKM_HEIGHT_OFFSET, height);
+}
+
+// Check if a PKM header is correctly formatted.
+
+bool etc1_pkm_is_valid(const etc1_byte* pHeader) {
+    if (memcmp(pHeader, kMagic, sizeof(kMagic))) {
+        return false;
+    }
+    etc1_uint32 format = readBEUint16(pHeader + ETC1_PKM_FORMAT_OFFSET);
+    etc1_uint32 encodedWidth = readBEUint16(pHeader + ETC1_PKM_ENCODED_WIDTH_OFFSET);
+    etc1_uint32 encodedHeight = readBEUint16(pHeader + ETC1_PKM_ENCODED_HEIGHT_OFFSET);
+    etc1_uint32 width = readBEUint16(pHeader + ETC1_PKM_WIDTH_OFFSET);
+    etc1_uint32 height = readBEUint16(pHeader + ETC1_PKM_HEIGHT_OFFSET);
+    return format == ETC1_RGB_NO_MIPMAPS &&
+            encodedWidth >= width && encodedWidth - width < 4 &&
+            encodedHeight >= height && encodedHeight - height < 4;
+}
+
+// Read the image width from a PKM header
+
+etc1_uint32 etc1_pkm_get_width(const etc1_byte* pHeader) {
+    return readBEUint16(pHeader + ETC1_PKM_WIDTH_OFFSET);
+}
+
+// Read the image height from a PKM header
+
+etc1_uint32 etc1_pkm_get_height(const etc1_byte* pHeader){
+    return readBEUint16(pHeader + ETC1_PKM_HEIGHT_OFFSET);
+}

third_party/android_opengl/etc1/etc1.h

@@ -35,4 +35,24 @@ bool etc1_encode_image(const unsigned char* pIn, unsigned int width, unsigned in
          unsigned int pixelSize, unsigned int stride, unsigned char* pOut, unsigned int outWidth,
          unsigned int outHeight);
 
+// Size of a PKM header, in bytes.
+
+#define ETC_PKM_HEADER_SIZE 16
+
+// Format a PKM header
+
+void etc1_pkm_format_header(unsigned char* pHeader, unsigned int width, unsigned int height);
+
+// Check if a PKM header is correctly formatted.
+
+bool etc1_pkm_is_valid(const unsigned char* pHeader);
+
+// Read the image width from a PKM header
+
+unsigned int etc1_pkm_get_width(const unsigned char* pHeader);
+
+// Read the image height from a PKM header
+
+unsigned int etc1_pkm_get_height(const unsigned char* pHeader);
+
 #endif // THIRD_PARTY_ANDROID_OPENGL_ETC1_ETC1_H_