--- a/configure.in
+++ b/configure.in
@@ -1859,65 +1859,46 @@ if test "$GNU_CC"; then
     fi
     WARNINGS_AS_ERRORS='-Werror'
     DSO_CFLAGS=''
     DSO_PIC_CFLAGS='-fPIC'
     ASFLAGS="$ASFLAGS -fPIC"
     _MOZ_RTTI_FLAGS_ON=-frtti
     _MOZ_RTTI_FLAGS_OFF=-fno-rtti
 
-    # Turn on GNU-specific warnings:
-    # -Wall - turn on a lot of warnings
-    # -pedantic - this is turned on below
-    # -Wpointer-arith - enabled with -pedantic, but good to have even if not
-    # -Werror=declaration-after-statement - MSVC doesn't like these
-    # -Wempty-body - catches bugs, e.g. "if (c); foo();", few false positives
-    #
-    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wall -Wpointer-arith -Wdeclaration-after-statement -Wempty-body"
-    
-    # Turn off the following warnings that -Wall/-pedantic turn on:
-    # -Woverlength-strings - we exceed the minimum maximum length all the time
-    #
-    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wno-overlength-strings"
-
+    # Turn on GNU specific features
+    # -Wall - turn on all warnings
+    # -pedantic - make compiler warn about non-ANSI stuff, and
+    #             be a little bit stricter
+    # -Wdeclaration-after-statement - MSVC doesn't like these
+    # Warnings slamm took out for now (these were giving more noise than help):
+    # -Wbad-function-cast - warns when casting a function to a new return type
+    # -Wshadow - removed because it generates more noise than help --pete
+    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wall -W -Wno-unused -Wpointer-arith -Wdeclaration-after-statement"
     if test -z "$INTEL_CC" -a -z "$CLANG_CC"; then
        # Don't use -Wcast-align with ICC or clang
        case "$CPU_ARCH" in
            # And don't use it on hppa, ia64, sparc, arm, since it's noisy there
            hppa | ia64 | sparc | arm)
            ;;
            *)
         _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wcast-align"
            ;;
        esac
     fi
 
     dnl Turn pedantic on but disable the warnings for long long
     _PEDANTIC=1
 
+    if test -z "$INTEL_CC"; then
+      _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -W"
+    fi
+
     _DEFINES_CFLAGS='-include $(DEPTH)/mozilla-config.h -DMOZILLA_CLIENT'
     _USE_CPP_INCLUDE_FLAG=1
-
-    AC_CACHE_CHECK(whether the compiler supports -Wtype-limits,
-                   ac_cc_has_wtype_limits,
-        [
-            AC_LANG_SAVE
-            AC_LANG_C
-            _SAVE_CFLAGS="$CFLAGS"
-            CFLAGS="$CFLAGS -Wtype-limits"
-            AC_TRY_COMPILE([],
-                           [return(0);],
-                           ac_cc_has_wtype_limits="yes",
-                           ac_cc_has_wtype_limits="no")
-            CFLAGS="$_SAVE_CFLAGS"
-            AC_LANG_RESTORE
-        ])
-    if test "$ac_cc_has_wtype_limits" = "yes"; then
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wtype-limits"
-    fi
 elif test "$SOLARIS_SUNPRO_CC"; then
     DSO_CFLAGS=''
     if test "$CPU_ARCH" = "sparc"; then
         # for Sun Studio on Solaris/SPARC
         DSO_PIC_CFLAGS='-xcode=pic32'
     else
         DSO_PIC_CFLAGS='-KPIC'
     fi
@@ -1935,32 +1916,18 @@ else
     DSO_CFLAGS=''
     DSO_PIC_CFLAGS='-KPIC'
     _DEFINES_CFLAGS='$(ACDEFINES) -D_MOZILLA_CONFIG_H_ -DMOZILLA_CLIENT'
 fi
 
 if test "$GNU_CXX"; then
     # FIXME: Let us build with strict aliasing. bug 414641.
     CXXFLAGS="$CXXFLAGS -fno-exceptions -fno-strict-aliasing"
-
-    # Turn on GNU-specific warnings:
-    # -Wall - turn on a lot of warnings
-    # -pedantic - this is turned on below
-    # -Wpointer-arith - enabled with -pedantic, but good to have even if not
-    # -Woverloaded-virtual - ???
-    # -Wempty-body - catches bugs, e.g. "if (c); foo();", few false positives
-    #
-    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wall -Wpointer-arith -Woverloaded-virtual -Wempty-body"
-
-    # Turn off the following warnings that -Wall/-pedantic turn on:
-    # -Woverlength-strings - we exceed the minimum maximum length all the time
-    # -Wctor-dtor-privacy - ???
-    #
-    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wno-overlength-strings -Wno-ctor-dtor-privacy"
-
+    # Turn on GNU specific features
+    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wall -Wpointer-arith -Woverloaded-virtual -Wsynth -Wno-ctor-dtor-privacy -Wno-non-virtual-dtor"
     if test -z "$INTEL_CXX" -a -z "$CLANG_CXX"; then
        # Don't use -Wcast-align with ICC or clang
        case "$CPU_ARCH" in
            # And don't use it on hppa, ia64, sparc, arm, since it's noisy there
            hppa | ia64 | sparc | arm)
            ;;
            *)
         _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wcast-align"
@@ -2051,34 +2018,16 @@ if test "$GNU_CXX"; then
                            ac_has_werror_return_type="no")
             CXXFLAGS="$_SAVE_CXXFLAGS"
             AC_LANG_RESTORE
         ])
     if test "$ac_has_werror_return_type" = "yes"; then
         _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=return-type"
     fi
 
-    AC_CACHE_CHECK(whether the compiler supports -Wtype-limits,
-                   ac_has_wtype_limits,
-        [
-            AC_LANG_SAVE
-            AC_LANG_CPLUSPLUS
-            _SAVE_CXXFLAGS="$CXXFLAGS"
-            CXXFLAGS="$CXXFLAGS -Wtype-limits"
-            AC_TRY_COMPILE([],
-                           [return(0);],
-                           ac_has_wtype_limits="yes",
-                           ac_has_wtype_limits="no")
-            CXXFLAGS="$_SAVE_CXXFLAGS"
-            AC_LANG_RESTORE
-        ])
-    if test "$ac_has_wtype_limits" = "yes"; then
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wtype-limits"
-    fi
-
 else
     _DEFINES_CXXFLAGS='-DMOZILLA_CLIENT -D_MOZILLA_CONFIG_H_ $(ACDEFINES)'
 fi
 
 dnl gcc can come with its own linker so it is better to use the pass-thru calls
 dnl MKSHLIB_FORCE_ALL is used to force the linker to include all object
 dnl files present in an archive. MKSHLIB_UNFORCE_ALL reverts the linker to
 dnl normal behavior.

--- a/content/xslt/src/base/txExpandedNameMap.h
+++ b/content/xslt/src/base/txExpandedNameMap.h
@@ -97,26 +97,28 @@ protected:
 
         bool next()
         {
             return ++mCurrentPos < mMap.mItems.Length();
         }
 
         const txExpandedName key()
         {
-            NS_ASSERTION(mCurrentPos < mMap.mItems.Length(),
+            NS_ASSERTION(mCurrentPos >= 0 &&
+                         mCurrentPos < mMap.mItems.Length(),
                          "invalid position in txExpandedNameMap::iterator");
             return txExpandedName(mMap.mItems[mCurrentPos].mNamespaceID,
                                   mMap.mItems[mCurrentPos].mLocalName);
         }
 
     protected:
         void* itemValue()
         {
-            NS_ASSERTION(mCurrentPos < mMap.mItems.Length(),
+            NS_ASSERTION(mCurrentPos >= 0 &&
+                         mCurrentPos < mMap.mItems.Length(),
                          "invalid position in txExpandedNameMap::iterator");
             return mMap.mItems[mCurrentPos].mValue;
         }
 
     private:
         txExpandedNameMap_base& mMap;
         PRUint32 mCurrentPos;
     };

deleted file mode 100644
--- a/gfx/ycbcr/QuellGccWarnings.patch
+++ /dev/null
@@ -1,40 +0,0 @@
-diff --git a/gfx/ycbcr/yuv_convert.cpp b/gfx/ycbcr/yuv_convert.cpp
---- a/gfx/ycbcr/yuv_convert.cpp
-+++ b/gfx/ycbcr/yuv_convert.cpp
-@@ -337,16 +337,17 @@ NS_GFX_(void) ScaleYCbCrToRGB32(const ui
-                                          source_dx_uv >> kFractionBits);
-         }
-       }
-       else {
-         ScaleYUVToRGB32Row_C(y_ptr, u_ptr, v_ptr,
-                              dest_pixel, width, source_dx);
-       }
- #else
-+      (void)source_dx_uv;
-       ScaleYUVToRGB32Row(y_ptr, u_ptr, v_ptr,
-                          dest_pixel, width, source_dx);
- #endif
-     }
-   }
-   // MMX used for FastConvertYUVToRGB32Row and FilterRows requires emms.
-   if (has_mmx)
-     EMMS();
-diff --git a/gfx/ycbcr/yuv_row.h b/gfx/ycbcr/yuv_row.h
---- a/gfx/ycbcr/yuv_row.h
-+++ b/gfx/ycbcr/yuv_row.h
-@@ -129,14 +129,14 @@ extern SIMD_ALIGNED(int16 kCoefficientsR
- #if defined(ARCH_CPU_X86) && !defined(ARCH_CPU_X86_64)
- #if defined(_MSC_VER)
- #define EMMS() __asm emms
- #pragma warning(disable: 4799)
- #else
- #define EMMS() asm("emms")
- #endif
- #else
--#define EMMS()
-+#define EMMS() ((void)0)
- #endif
- 
- }  // extern "C"
- 
- #endif  // MEDIA_BASE_YUV_ROW_H_

--- a/gfx/ycbcr/README
+++ b/gfx/ycbcr/README
@@ -20,10 +20,8 @@ convert.patch contains the following cha
   * Add YCbCr 4:4:4 support
   * Bug 619178 - Update CPU detection in yuv_convert to new SSE.h interface.
   * Bug 616778 - Split yuv_convert FilterRows vectorized code into separate files so it can
     be properly guarded with cpuid() calls.
 
 win64.patch: SSE2 optimization for Microsoft Visual C++ x64 version
 
 TypeFromSize.patch: Bug 656185 - Add a method to detect YUVType from plane sizes.
-
-QuellGccWarnings.patch: Bug 711895 - Avoid some GCC compilation warnings.

--- a/gfx/ycbcr/update.sh
+++ b/gfx/ycbcr/update.sh
@@ -4,9 +4,8 @@ cp $1/media/base/yuv_convert.cc yuv_conv
 cp $1/media/base/yuv_row.h .
 cp $1/media/base/yuv_row_table.cc yuv_row_table.cpp
 cp $1/media/base/yuv_row_posix.cc yuv_row_posix.cpp
 cp $1/media/base/yuv_row_win.cc yuv_row_win.cpp
 cp $1/media/base/yuv_row_posix.cc yuv_row_c.cpp
 patch -p3 <convert.patch
 patch -p3 <win64.patch
 patch -p3 <TypeFromSize.patch
-patch -p3 <QuellGccWarnings.patch

--- a/gfx/ycbcr/yuv_convert.cpp
+++ b/gfx/ycbcr/yuv_convert.cpp
@@ -337,17 +337,16 @@ NS_GFX_(void) ScaleYCbCrToRGB32(const ui
                                          source_dx_uv >> kFractionBits);
         }
       }
       else {
         ScaleYUVToRGB32Row_C(y_ptr, u_ptr, v_ptr,
                              dest_pixel, width, source_dx);
       }
 #else
-      (void)source_dx_uv;
       ScaleYUVToRGB32Row(y_ptr, u_ptr, v_ptr,
                          dest_pixel, width, source_dx);
 #endif
     }
   }
   // MMX used for FastConvertYUVToRGB32Row and FilterRows requires emms.
   if (has_mmx)
     EMMS();

--- a/gfx/ycbcr/yuv_row.h
+++ b/gfx/ycbcr/yuv_row.h
@@ -129,14 +129,14 @@ extern SIMD_ALIGNED(int16 kCoefficientsR
 #if defined(ARCH_CPU_X86) && !defined(ARCH_CPU_X86_64)
 #if defined(_MSC_VER)
 #define EMMS() __asm emms
 #pragma warning(disable: 4799)
 #else
 #define EMMS() asm("emms")
 #endif
 #else
-#define EMMS() ((void)0)
+#define EMMS()
 #endif
 
 }  // extern "C"
 
 #endif  // MEDIA_BASE_YUV_ROW_H_

--- a/js/src/configure.in
+++ b/js/src/configure.in
@@ -1801,65 +1801,45 @@ if test "$GNU_CC"; then
     fi
     WARNINGS_AS_ERRORS='-Werror'
     DSO_CFLAGS=''
     DSO_PIC_CFLAGS='-fPIC'
     ASFLAGS="$ASFLAGS -fPIC"
     _MOZ_RTTI_FLAGS_ON=-frtti
     _MOZ_RTTI_FLAGS_OFF=-fno-rtti
 
-    # Turn on GNU-specific warnings:
-    # -Wall - turn on a lot of warnings
-    # -pedantic - this is turned on below
-    # -Wpointer-arith - enabled with -pedantic, but good to have even if not
-    # -Wdeclaration-after-statement - MSVC doesn't like these
-    # -Wempty-body - catches bugs, e.g. "if (c); foo();", few false positives
-    #
-    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wall -Wpointer-arith -Wdeclaration-after-statement -Wempty-body"
-    
-    # Turn off the following warnings that -Wall/-pedantic turn on:
-    # -Woverlength-strings - we exceed the minimum maximum length all the time
-    #
-    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wno-overlength-strings"
-
+    # Turn on GNU specific features
+    # -Wall - turn on all warnings
+    # -pedantic - make compiler warn about non-ANSI stuff, and
+    #             be a little bit stricter
+    # Warnings slamm took out for now (these were giving more noise than help):
+    # -Wbad-function-cast - warns when casting a function to a new return type
+    # -Wshadow - removed because it generates more noise than help --pete
+    _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wall -W -Wno-unused -Wpointer-arith"
     if test -z "$INTEL_CC" -a -z "$CLANG_CC"; then
        # Don't use -Wcast-align with ICC or clang
        case "$CPU_ARCH" in
            # And don't use it on hppa, ia64, sparc, arm, since it's noisy there
            hppa | ia64 | sparc | arm)
            ;;
            *)
         _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wcast-align"
            ;;
        esac
     fi
 
     dnl Turn pedantic on but disable the warnings for long long
     _PEDANTIC=1
 
+    if test -z "$INTEL_CC"; then
+      _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -W"
+    fi
+
     _DEFINES_CFLAGS='-include $(DEPTH)/js-confdefs.h -DMOZILLA_CLIENT'
     _USE_CPP_INCLUDE_FLAG=1
-
-    AC_CACHE_CHECK(whether the compiler supports -Wtype-limits,
-                   ac_cc_has_wtype_limits,
-        [
-            AC_LANG_SAVE
-            AC_LANG_C
-            _SAVE_CFLAGS="$CFLAGS"
-            CFLAGS="$CFLAGS -Wtype-limits"
-            AC_TRY_COMPILE([],
-                           [return(0);],
-                           ac_cc_has_wtype_limits="yes",
-                           ac_cc_has_wtype_limits="no")
-            CFLAGS="$_SAVE_CFLAGS"
-            AC_LANG_RESTORE
-        ])
-    if test "$ac_cc_has_wtype_limits" = "yes"; then
-        _WARNINGS_CFLAGS="${_WARNINGS_CFLAGS} -Wtype-limits"
-    fi
 elif test "$SOLARIS_SUNPRO_CC"; then
     DSO_CFLAGS=''
     if test "$CPU_ARCH" = "sparc"; then
         # for Sun Studio on Solaris/SPARC
         DSO_PIC_CFLAGS='-xcode=pic32'
     else
         DSO_PIC_CFLAGS='-KPIC'
     fi
@@ -1875,31 +1855,18 @@ else
     fi
 
     DSO_CFLAGS=''
     DSO_PIC_CFLAGS='-KPIC'
     _DEFINES_CFLAGS='$(ACDEFINES) -D_JS_CONFDEFS_H_ -DMOZILLA_CLIENT'
 fi
 
 if test "$GNU_CXX"; then
-    # Turn on GNU-specific warnings:
-    # -Wall - turn on a lot of warnings
-    # -pedantic - this is turned on below
-    # -Wpointer-arith - enabled with -pedantic, but good to have even if not
-    # -Woverloaded-virtual - ???
-    # -Wempty-body - catches bugs, e.g. "if (c); foo();", few false positives
-    #
-    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wall -Wpointer-arith -Woverloaded-virtual -Wempty-body"
-
-    # Turn off the following warnings that -Wall/-pedantic turn on:
-    # -Woverlength-strings - we exceed the minimum maximum length all the time
-    # -Wctor-dtor-privacy - ???
-    #
-    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wno-overlength-strings -Wno-ctor-dtor-privacy"
-
+    # Turn on GNU specific features
+    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wall -Wpointer-arith -Woverloaded-virtual -Wsynth -Wno-ctor-dtor-privacy -Wno-non-virtual-dtor"
     if test -z "$INTEL_CXX" -a -z "$CLANG_CXX"; then
        # Don't use -Wcast-align with ICC or clang
        case "$CPU_ARCH" in
            # And don't use it on hppa, ia64, sparc, arm, since it's noisy there
            hppa | ia64 | sparc | arm)
            ;;
            *)
         _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wcast-align"
@@ -1990,34 +1957,16 @@ if test "$GNU_CXX"; then
                            ac_has_werror_return_type="no")
             CXXFLAGS="$_SAVE_CXXFLAGS"
             AC_LANG_RESTORE
         ])
     if test "$ac_has_werror_return_type" = "yes"; then
         _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Werror=return-type"
     fi
 
-    AC_CACHE_CHECK(whether the compiler supports -Wtype-limits,
-                   ac_has_wtype_limits,
-        [
-            AC_LANG_SAVE
-            AC_LANG_CPLUSPLUS
-            _SAVE_CXXFLAGS="$CXXFLAGS"
-            CXXFLAGS="$CXXFLAGS -Wtype-limits"
-            AC_TRY_COMPILE([],
-                           [return(0);],
-                           ac_has_wtype_limits="yes",
-                           ac_has_wtype_limits="no")
-            CXXFLAGS="$_SAVE_CXXFLAGS"
-            AC_LANG_RESTORE
-        ])
-    if test "$ac_has_wtype_limits" = "yes"; then
-        _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wtype-limits"
-    fi
-
 else
     _DEFINES_CXXFLAGS='-DMOZILLA_CLIENT -D_JS_CONFDEFS_H_ $(ACDEFINES)'
 fi
 
 dnl gcc can come with its own linker so it is better to use the pass-thru calls
 dnl MKSHLIB_FORCE_ALL is used to force the linker to include all object
 dnl files present in an archive. MKSHLIB_UNFORCE_ALL reverts the linker to
 dnl normal behavior.

--- a/js/src/jsarray.cpp
+++ b/js/src/jsarray.cpp
@@ -400,33 +400,20 @@ DoGetElement(JSContext *cx, JSObject *ob
     *hole = !present;
     if (*hole)
         vp->setUndefined();
 
     return true;
 }
 
 template<typename IndexType>
-static void
-AssertGreaterThanZero(IndexType index)
-{
-    JS_ASSERT(index >= 0);
-}
-
-template<>
-void
-AssertGreaterThanZero(jsuint index)
-{
-}
-
-template<typename IndexType>
 static JSBool
 GetElement(JSContext *cx, JSObject *obj, IndexType index, JSBool *hole, Value *vp)
 {
-    AssertGreaterThanZero(index);
+    JS_ASSERT(index >= 0);
     if (obj->isDenseArray() && index < obj->getDenseArrayInitializedLength() &&
         !(*vp = obj->getDenseArrayElement(uint32_t(index))).isMagic(JS_ARRAY_HOLE)) {
         *hole = JS_FALSE;
         return JS_TRUE;
     }
     if (obj->isArguments()) {
         if (obj->asArguments()->getElement(uint32_t(index), vp)) {
             *hole = JS_FALSE;

--- a/js/src/jsgc.cpp
+++ b/js/src/jsgc.cpp
@@ -1337,17 +1337,17 @@ JSRuntime::setGCLastBytes(size_t lastByt
     size_t base = gckind == GC_SHRINK ? lastBytes : Max(lastBytes, GC_ALLOCATION_THRESHOLD);
     float trigger = float(base) * GC_HEAP_GROWTH_FACTOR;
     gcTriggerBytes = size_t(Min(float(gcMaxBytes), trigger));
 }
 
 void
 JSRuntime::reduceGCTriggerBytes(uint32_t amount) {
     JS_ASSERT(amount > 0);
-    JS_ASSERT(gcTriggerBytes >= amount);
+    JS_ASSERT(gcTriggerBytes - amount >= 0);
     if (gcTriggerBytes - amount < GC_ALLOCATION_THRESHOLD * GC_HEAP_GROWTH_FACTOR)
         return;
     gcTriggerBytes -= amount;
 }
 
 void
 JSCompartment::setGCLastBytes(size_t lastBytes, JSGCInvocationKind gckind)
 {
@@ -1356,17 +1356,17 @@ JSCompartment::setGCLastBytes(size_t las
     size_t base = gckind == GC_SHRINK ? lastBytes : Max(lastBytes, GC_ALLOCATION_THRESHOLD);
     float trigger = float(base) * GC_HEAP_GROWTH_FACTOR;
     gcTriggerBytes = size_t(Min(float(rt->gcMaxBytes), trigger));
 }
 
 void
 JSCompartment::reduceGCTriggerBytes(uint32_t amount) {
     JS_ASSERT(amount > 0);
-    JS_ASSERT(gcTriggerBytes >= amount);
+    JS_ASSERT(gcTriggerBytes - amount >= 0);
     if (gcTriggerBytes - amount < GC_ALLOCATION_THRESHOLD * GC_HEAP_GROWTH_FACTOR)
         return;
     gcTriggerBytes -= amount;
 }
 
 namespace js {
 namespace gc {
 

--- a/js/src/jstypedarray.cpp
+++ b/js/src/jstypedarray.cpp
@@ -1682,17 +1682,19 @@ class TypedArrayTemplate
 
     static void copyIndexToValue(JSContext *cx, JSObject *tarray, uint32_t index, Value *vp);
 
     static JSObject *
     createSubarray(JSContext *cx, JSObject *tarray, uint32_t begin, uint32_t end)
     {
         JS_ASSERT(tarray);
 
+        JS_ASSERT(0 <= begin);
         JS_ASSERT(begin <= getLength(tarray));
+        JS_ASSERT(0 <= end);
         JS_ASSERT(end <= getLength(tarray));
 
         JSObject *bufobj = getBuffer(tarray);
         JS_ASSERT(bufobj);
 
         JS_ASSERT(begin <= end);
         uint32_t length = end - begin;
 

--- a/layout/generic/nsHTMLReflowMetrics.h
+++ b/layout/generic/nsHTMLReflowMetrics.h
@@ -66,21 +66,21 @@ enum nsOverflowType { eVisualOverflow, e
   for (nsOverflowType var_ = nsOverflowType(0); var_ < 2;                     \
        var_ = nsOverflowType(var_ + 1))
 
 struct nsOverflowAreas {
 private:
   nsRect mRects[2];
 public:
   nsRect& Overflow(size_t aIndex) {
-    NS_ASSERTION(aIndex < 2, "index out of range");
+    NS_ASSERTION(0 <= aIndex && aIndex < 2, "index out of range");
     return mRects[aIndex];
   }
   const nsRect& Overflow(size_t aIndex) const {
-    NS_ASSERTION(aIndex < 2, "index out of range");
+    NS_ASSERTION(0 <= aIndex && aIndex < 2, "index out of range");
     return mRects[aIndex];
   }
 
   nsRect& VisualOverflow() { return mRects[eVisualOverflow]; }
   const nsRect& VisualOverflow() const { return mRects[eVisualOverflow]; }
 
   nsRect& ScrollableOverflow() { return mRects[eScrollableOverflow]; }
   const nsRect& ScrollableOverflow() const { return mRects[eScrollableOverflow]; }